The proper road bike (frame) fit with long legs (short torso) and possible solution I've found

[silvalis]

For those shoes, saddle is probably a touch low
I don't particularly think you are sitting too far forward, but I'm of the 'sit forward' school of thought.

Probably not really a good idea to take a random stab at torso angle on the hoods, especially since your original complaints were sore knees, sore elbows.

Out of interest - knees - inside, outside or front pain?

[alcatraz]

It's a good size frame for an allrounder.

It won't be nice in the tt position and at speed because the wheelbase is too short I think. I'm 176/82inseam and 97cm wheelbase is too short for riding in the aero position.

It's fine for normal riding.

If you can't relax in the aero bars because the bike is twitching like crazy at 50km/h you can't stay in that position. Kind of a waste.

Sure you could stay in it on perfect roads and perfect wind conditions for a limited time, enough to maybe get a PR on strava but remember that to be fast in the aero position you need hundreds or maybe thousands of km in this position.

I suggest to go with two bikes if you need an aero position frame. Maybe a custom frame would be of interest? I'd look at the cervelo p-series geometry and see if they have something.

Also by building a bike that does both, one problem is the knees hitting the aero pads if you try to go out of saddle and a maybe too extreme forward position if you want to ride normally. The seat angle is hard to get right too as you might want to angle down for tt but more flat for road. Also raising the elbow pads high enough is a problem. They are pointless if they are at the height of the bars. Too big of a transition, body will never adjust to it, no power. Also it's annoying not being able to shift from the aero position or drink.

[spartacus]

What is your saddle height?

[Primorsky]

For those shoes, saddle is probably a touch low
I don't particularly think you are sitting too far forward, but I'm of the 'sit forward' school of thought.
Probably not really a good idea to take a random stab at torso angle on the hoods, especially since your original complaints were sore knees, sore elbows.

Speaking of an old bike, I am sure that my complaints about elbows (which are in a "locked" position most time of ride) comes from an incorrect frame size of the frame and stem (ETT=580, stem 100mm). Now I get the 90mm stem and "ultra" compact bar with 65 mm reach. I hope it gets better now. If not, the only solution will be to get another bike...

On this new Milano72 bike my torso angle is 46-47 deg (hands on hoods), as roughly measured from my other private photos where I am sitting with the same settings of bicycle. A bit "relaxed" angle, I guess.

Out of interest - knees - inside, outside or front pain?

More likely, front-inside pain. I guess I had this due to incorrect fore aft saddle position. Actually, I've tried to compensate a long reach to bar with the saddle setting. After all,l it was painful for knees on a distance. Now, I did some correction (moving the knee-joint to the pedal axis on flat pedals) and my knees feel much better. At least, after a few test rides on trainer.

It's a good size frame for an allrounder.
It won't be nice in the tt position and at speed because the wheelbase is too short I think. I'm 176/82inseam and 97cm wheelbase is too short for riding in the aero position.
It's fine for normal riding.
If you can't relax in the aero bars because the bike is twitching like crazy at 50km/h you can't stay in that position. Kind of a waste.
Sure you could stay in it on perfect roads and perfect wind conditions for a limited time, enough to maybe get a PR on strava but remember that to be fast in the aero position you need hundreds or maybe thousands of km in this position.
I suggest to go with two bikes if you need an aero position frame. Maybe a custom frame would be of interest? I'd look at the cervelo p-series geometry and see if they have something.
Also by building a bike that does both, one problem is the knees hitting the aero pads if you try to go out of saddle and a maybe too extreme forward position if you want to ride normally. The seat angle is hard to get right too as you might want to angle down for tt but more flat for road. Also raising the elbow pads high enough is a problem. They are pointless if they are at the height of the bars. Too big of a transition, body will never adjust to it, no power. Also it's annoying not being able to shift from the aero position or drink.

Thanks for your input. Yes, I realize that a "conventional" road bike (of any brand or any model) can't be converted to a full value TT-bike. I have no interest in a dedicated TT machine yet.
I live in windy and flat area, so the 50km/h speed mark likely wouldn't be a typical scenario (but well, who knows). If I'm not mistaken, a TT-bikes doesn't have a significantly longer wheelbase. What's makes them more stable on a high speeds is the specific frame/fork geometry and rider's position. Not considering myself as the "Strava racer" too. At least, at moment . I hope that the dual-position(quickly switchable) seat post will allow to get a better seat angles / saddle's forward position when on aero bars. Also, it should help to avoid knees hitting the pads when on "conventional road" position. As for the elbow pads height, ok (i get it). Looks like the proper TT-position is another, complicated story.

What is your saddle height?

81.5 cm (top of the saddle -> bottom-bracket axle). Cranks 172.5.

[PokojniToza]

I think you need to go a size up. Or at least use a longer stem. Take it with a bag of salt, though.

[silvalis]

For those shoes, saddle is probably a touch low
I don't particularly think you are sitting too far forward, but I'm of the 'sit forward' school of thought.
Probably not really a good idea to take a random stab at torso angle on the hoods, especially since your original complaints were sore knees, sore elbows.

Speaking of an old bike, I am sure that my complaints about elbows (which are in a "locked" position most time of ride) comes from an incorrect frame size of the frame and stem (ETT=580, stem 100mm). Now I get the 90mm stem and "ultra" compact bar with 65 mm reach. I hope it gets better now. If not, the only solution will be to get another bike...

On this new Milano72 bike my torso angle is 46-47 deg (hands on hoods), as roughly measured from my other private photos where I am sitting with the same settings of bicycle. A bit "relaxed" angle, I guess.

Out of interest - knees - inside, outside or front pain?

More likely, front-inside pain. I guess I had this due to incorrect fore aft saddle position. Actually, I've tried to compensate a long reach to bar with the saddle setting. After all,l it was painful for knees on a distance. Now, I did some correction (moving the knee-joint to the pedal axis on flat pedals) and my knees feel much better. At least, after a few test rides on trainer.

Looking at the previous posts and pictures again, I don't really think that your elbow issues are due to incorrect sizing - probably more just inexperience (you really just have to train the habit and force your core to do the work). I mean, if you look at what you're trying to do with the new bike and long stem, you're going to pretty much end up with similar reach to the old bike

on knees: i guess you moved it backwards. Remember, if you move your saddle forwards you also have to move it upwards.

[wheelsONfire]

There are myriads of options.
There is this theory of always having the "centre" of the cleat positioned forward of the pedal axle, no matter where on the pedal stroke.
If one use this method, the saddle goes more forward (atleast for me).
Easy method is also sitting on the saddle and drop left/right leg horizontal with foot in level.
The heel should lightly touch the top of the pedal (this should be with the bike shoes on).
These two in conjunction, would give you a theoretical saddle seatback and height.