Ground Control with Momentary in expression?

[Piplodocus]

My great behemoth of a board (including px-8, midi clock pedals and other midi controllers + loads of pedals) is too much for just basic stuff where all i need is delay/verb. My Strymon Timeline, Bigsky and midi amp switcher are all I need, which live in a little rack on top the amp anyway. So I've regularly been leaving the big board at home and going back to controlling the whole rig with just my super useful Ground Control (old, non-Pro FW v2.5) via a single MIDI lead/phantom power. I have it in 10-patch mode as I just want presets basically (only using clean/crunch/lead with appropriate amounts of verb + the same 3 with delay in = 6 patches). The only thing lacking is a tap tempo for the delay.

Is there any way I can have just 1 button be a MIDI CC? I presume not?

So I tried sticking a momentary switch pedal I have here in the expression jack and assigning it to CC81(?). It looks all dandy, but the strymon goes silly fast no matter what speed I try. Sticking it through a MIDI monitor it appears it sends 6 CC value 0 on pedal down, and 6 CC value 127 on pedal up. I presume because normally it would be trying to fit at least 6 different values in on a continuous sweep pedal for smoothness. I guess this is confusing the Timeline and thinking I have a lightning-fast 6-tap foot and doesn't look for a pedal up between taps. So it just counts incoming value 0s for timing. Any way to make it only send one down on down and one up on up? I tried the fast and normal expression speeds and they both give 6. If not any other ideas (I know there's supposed to be some kinda sequencer start option, but couldn't understand that, and not sure it has assignable CC anyway)?

Otherwise I'd have to have 4 patches per bank when I need 6, and 5 unused CC stomps. Or just try get a different momentary switch that's compatible with the Strymon tap input, and get another stereo cable for it out to stage front, as the Strymon doesn't like a simple mono-cable momentary.