Bike Mielec

Track classic have a normal 73 degree ST (54cm), the MASH have a 76 degree ST (medium), a massive 3 degrees steeper, meaning approx 3cm longer theoretical top tube with the saddle in the right position.

Only solution is a seatpost with a massive layback, but that'd mean you'll need a shorter stem than you usually have on your Fuji.

The seat post on my fuji has a fair bit of setback and I'm using an inline on the Mielec (not sure why...) so I might see how I get on with something with a bit more setback if I find the top tube seems too short.