He’s using the Toughbox Mini’s, which have the same gearing as a normal Toughbox with a plastic case (14:50 twice for 1:12.75 total reduction). He looks to be going ~2:1 up again, maybe more.
If we guess he’s going 2:1 up in belts, with the 1:2.25 final drive ratio in the Revolution 2, he will go at a peak speed of around 6ft/sec assuming no speed loss.
If he were to mount a pulley directly on the CIM, and a larger pulley on the Revolution crab pod, without the gearbox at all, let’s see what we could get:
-I am using 25 chain sizes since I am more familiar with the available AndyMark offerings for sprockets than the Gates pulley sizes.
CIM sprocket: 10t CIM bore (AM part here)
Crab pod sprocket: 32t plate (assuming with AM hub) (AM part here)
The math now says 12.87 ft/sec with no speed loss. With realistic speed losses for two stages of chain reduction, and generally good build quality (90% efficiency in speed), we can get a more realistic number of 11.58 ft/sec, which is in the ballpark of where you probably want to be.
As for the plate, it looks like he’s using the Revolution Mounting System from Team221, or something very similar. I would still try to mount that crab pod better, possibly mount it to another face (such as the front/back beam). You could alternatively make a moderately thick end beam bracket to replace the corner triangles and crab pod mount with a single piece of plate.
It does look like you’ve put a lot of thought into the manufacturing and mechanical design.