I normally ride a 50-52CM (I have both) as a racing/commuter bike. I have been looking at touring bikes for a trip next summer, and was wondering if sizing was different. Someone told me I should take into account that I would be lowering the seat post height on a touring bike, so I should look at a larger frame size. As far as I understand, standover height is the key. Does what he says make sense? Are they usually different?