I have enjoyed playing cornet for a number of years. After buying used instruments, cleaning/fixing/learning about them, I eventually settled on a Bach CR310 as my favorite. I use a Bach 5B mouthpiece, finding it the best balance for me, for the kind of music I play and the tone I like. I have long admired the French Horn sound, having bought a single F and a single Bb on EBay in the last six months. I wondered if there were a way I could pick that up as well, without letting go of my cornet. Having tried several horns and mouthpieces (same process as with cornets, I found that a Bach 16S FH mpc is very similar in cup diameter and rim shape to the Bach 5B (cornet). I have been using it with an adapter on my cornet, getting a nice FH-like tone. But as I tire, it gets harder to push air through the horn. I'm probably not understanding how backbore, cup depth, and natural resistance differences between the horns. Cornet is about 54" through open valves, not sure of avg diameter. FH is either 144" or 96" and wrapped tighter. And I've learned that it takes a while to really compare mouthpiece performance on any horn. Can what I'm trying to do be done? Should I just practice on each horn separately-say one in the morning and the other in the evening? Thanks for any input.