Hello Foil owners,
I'm between two sizes on Scott Foil. 54 and 56. I would like most the 54 stack and reach, but I wonder is the seatpost long enough.
I would need 73cm from center of bb to the sadle rails.

I'm in the same situation as you. Buying Foil between sizes 54-56... Toptube on 54 is actually 55cm long, so I've decided for 54. It's also easier to get agressive position on smaller frame.

I think that seatpost lenght shoudn't be a problem

Just bought a Foil in a 54. On mine there is 71.5cm from center of bb to the saddle rails with less than 20cm of seatpost showing so you'll have more than enough adjustment.

What do you mean long enough? Set back or actual length? If length, it is a standard 300mm length.

Setback on the 54 comes stock with zero, 56 and above 20mm I believe.

I run a 56cm, switched from a 54. The 54, if you are 5'10" or taller with some longer arms etc...the 54 is going to be twitchy IMO. Even with a 120mm stem, it was way to short of a wheel base and top tube IMO. Never felt comfotable and always felt like I was up over the top of the frame instead of being more down/sitting as part of the bike lower.

Now I'm on a 56cm, with a shorter stem, more stable, but still turns plenty fast.

The only thing is with Scott I don't like and many manufacturers, except CDale, they jump too far from M/54 to L/56 frames. The head tube jumps from 140 to 160. I'm personally right in between, CDale has the perfect sizing with their 56cm for me personally, example headtube is 155mm, top tube is 555. Instead of going from 548mm to 568mm or Foil/Venge for example. But I sold my Supersix and went to a more aero/stiffer frame and settled on the Foil. So, after riding the smaller frame, it was too small.

My seat height is around 75-75.5mm from BB center to top of saddle on any size frame. Seat post still has 2/3rds left of length. You would need to be 6'5" to use all of that post.

Thank's to all so far,
I'm 180cm with 87cm legs and I drive 765cm saddle hight. But I have allways liked quite low hadlebar position. I believe I order 54. Hope that
seatpost is enough..In the picture you see my bike today. It's a German RedBull in size 57! If I go for 56 in Foil, I get about 1cm more reach, 1cm
more stack and 0,5 more wheelbase. In 54 I need only one spacer to get same position, if the seatpost is enough.

You'll be fine. I measure the same and it's perfect for me. Granted my insane morphology means I need a lower post and higher stem, but the Foil is absolutely incredible. Enjoy!