Originally Posted by
drunix
Exactly, if you use KOPS and a constant distance center of the BB to the top of the saddle, then you're going to end up with the same "effective" seat tube angle on any bike that you set up this way. However, the actual seat tube angle will determine how easy it is to get a KOPS fit (if that's your goal).
Dru
Even if you don't use KOPS, if you tilt the seat tube forward, to keep your butt/knee/BB relationship the way your body likes it, you'll have to move the seat back on the rails. The problem will come in if your saddle is already back pretty far on the more laid-back frame - there is such a thing as not being able to get enough setback.
Road Fan