I love gapless presets! This is my obsession with programming the Axe-FX III. I like having four Drive Blocks in parallel, then a Multiplexer, then two amps, then another Multiplexer. I also do not bypass anything, and I do not switch Channels for Drives or Amps; instead of Channels I use Scene Controllers, which can also be gapless, if you set each modifier for maximum speed (three settings to watch there). I create a spreadsheet for the settings that change between eight Scenes, calculating the Scene Controller settings for different values. You can then use altered modifier curves to assign multiple parameters to the same Scene Controller, up to 32 modifiers. It’s a son of a bitch to program, but totally with it, and utterly gapless.
If you search the forum for the term gapless in the title with my username, I’ve posted my spreadsheet calculations (Input Gain took some figuring). If you have any questions, let me know!