Right, I should change AUFX:Dub to save the SYNC toggle in the presets as well, so that you can set up a bunch of presets all with SYNC enabled. Another idea was to just leave SYNC in its current state when loading a preset, but then the problem is that it would break all the presets that depend on a very small delay time, like chorus and flanger effects etc. So I think it's better to save its state in the preset instead.
MIDI controllable tap-tempo is on my todo list for AUM. How would midi addressable tempo work?