Since I am 1,90 m tall and was allways riding a 58 I went with a 58. Reach is 10 mm more than my old bike so I took a 1 cm shorter stem with 110 mm.

I worked out.

What is your bottom bracket to seat height?

I am 180/181 cm tall and the saddle height is 82/83, I have more legs than bust. only 58. with a 350mm seat post, there would be 6-7cm left inside the frame. too few. as well as having a disproportionate saddle/handlebar height difference.
How do you ride on a 54 frame?

I'm at 192cm with a BB to the seat of 84cm, a 400mm seat post in a XL frame would work for me, but not a 350mm seat post...