Got it! What I was doing wrong was in command center. To properly assign midi commands to each individual footswitch in Snapshot mode, you have to select the Instant Command (Lightning Bolt), then actually push the footswitch you want to individually program, and assign a midi command to each one. Now it seems simple!
This is awesome because now I can go from clean to crunch to heavy without changing a preset, hence no "preset dropoff". Very cool...
Thanks for your help!