Originally Posted by 8aaron8

In order to maintain the same balance over the bike, yes you should maintain the same setback value. Regardless of the seat tube angle, the bb shell is in the parallel to the ground and your position over it is determined by the setback value. Sometimes, people may have to change from a setback seatpost to a straight seatpost as the ST angle gets more shallow so they can clamp the saddle in the center of the rails. As for the bike feeling different, assuming the top tubes on both bikes measure the same, technically the reach on the frame with a 72.5 seat tube angle will be shorter because as the seat tube moves backwards the head tube (connecting to the seat tube by the top tube) will move back as well. So you may need a longer stem to get your body weight further forward to compensate.