Hi Kevin,

Unfortunately the EFX's expression pedal feature will only transmit on one channel so there is no way to control boxes on that are assigned to different MIDI channels.  So that's a no go.  You'd have to go directly into the expression pedal jack on each timefactor either with one pedal per factor or a single pedal through some sort of switching to route the exp pedal to the selected factor.  I suppose one could plug in the expression pedal to input A or input B on the EFX and then use one bank of loops to route that to each of the four factor pedals' exp jacks but then you've consumed 4 loops.  Not sure that would work anyway.

If all the factors were set to listen to all MIDI channels then you could do it from a single exp pedal via the musicom but then of course you can't switch presets etc.

As for programming the range of the expression pedal, yes it appears you program a "toe up" sound and a "toe down" setting for each preset.  I haven't tried this yet as I'm not a big user of expression pedals.  But this looks to be something that is unique to plugging into the factor pedals' exp jack directly.  Doing expression via the EFX will only transmit a single CC on one channel and you can't customize the range.  Which is why I got a mix range of 0-100% when I tried it.