@fdegrove - i had a pair of the old Eurus Carbons. The Zondas are the closest thing you'll find now, albeit only in clincher format.
Unfortunately it is past tense for me as well. As the saying goes: you don't know what you have untill it's gone (or something along those lines).
It's only a few years back that I realised how uncomfortably stiff (in the vertical plane) most wheels have become when I picked up a few sets of Neutron for tubulars and a set of new style Eurus (tubs as well).
Compared to the old style Eurus the new ones felt unbelievably harsh.
Bottomline is that (and this is quite funny) I find wheels like Neutrons/ old Eurus etc. far easier to ride with (less fatigue inducing) and I can't say they were any slower. In fact I often find myself pushing bigger gears with Neutrons than with its carbon counterpart the Hyperons (which also happen to be quite a bit lighter).
I could be wrong but I can't help but feel that little bit of extra vertical compliance is actually a good thing to have in a wheel.
This is why I wonder why none of the bigger players (not looking at you Campagnolo
) seems to offer a wheelset that's targeted at the Gran Fondo style of rider (not necessarily competition but more high mileage at relatively high speed).
Something more allround than the good old Neutrons, a bit lighter is welcomed too and it may certainly be more aero.
I don't think a 32mm carbon rim would cut it as I often blame the carbon rims for lacking that little bit of vertical compliance that makes a wheel more forgiving rather than demanding if you see what I mean.
In short, some kind of wheel that does everything really well without killing you in the process and is actually a joy to ride instead of a pain like some wheels can be.
I am aware that some may think that if you train more it will become much easier to push the extremely stiff wheels and to a certain point I'd agree....
For those who have not spent serious time on a traditional build wheelset (quality shallow section alloy rim, 32 spokes, 3x rear, 2x front or similar) don't believe for a minute that bigger softer tires is the whole story. Yes tires are key but wheel type is very significant in what the road feels like on your feet, hands, and ass. You also get a much better sense of connectedness to the road in corners and on an rough surface. Combine the traditional build with wide rim tech and 25c tires and you are ready for anything. And at 1500 grams such wheels are still light enough and fast enough for racing.
That type of wheel perfectly describes the feeling and the joy of riding I'm looking for but it does not need to be so tradtional.
OTOH I always suggest to younger riders to at least give them a try just so they realise how much fun they can be.
Now imagine these wheels without the typical drawbacks such as weight and lack of aero. Would a wheel with a little bit more give in the vertical plane really be so much more inefficient? I really doubt it....