Sorry for the delay, here are a few photos of the beast.
Thanks to @Maxence for the donation of the saddle and brake support. You’ll also see a magnificent collector’s gold valve cap that I won at CFM2024. And the famous plastic pedals (look trail grip) that I really like.
The coterless steel cranks are 140mm long, so they just barely fit, you’d need a lot of Q-factor to use longer cranks.
The tire is 20x2.4, I took it because I wanted a bigger wheel 
, because with this frame, I can’t use a bigger rim. Anyway, with a hub like that, I think 24” would have been the max rim size.
Frame-crank clearance with 140mm:
The last photo illustrates the position I use to mount the beast: one foot on a pedal at the bottom (for me the right foot) and the other behind to push. I guess that’s how you mount on a BC wheel (I haven’t tried the BC yet).
I’m wondering if it’s possible to start up in a different position. I know that some freewheel riders mount by first putting their foot on the front pedal (with the cranks horizontal).
What about you @waaalrus, how did you mount this unicycle? Do you still have your x3.8 beast?