This weekend I made up some cables (would have preferred the Tesla ones but, still). I made 5-15/20, 6-15/20, 10-30 & duplex 5-15 to go with the existing 14-50/30 (a trick donauker taught me).
I tried the diode and found:
wht-green open: 12,15A
Diode (cathode to wht): 16A
Diode (cathode to grn): 24A
wht-green closed: 40A
I used this in my adapters to limit max current though I did see that voltage doesn't play a part and that the UMC was happy to set up 120V@40A. I tried a couple of zener diodes, 5.1V and 12V but they made no difference.
I also found out why the outlet on the front of my house doesn't work; they've transposed hot/ground on the 120v outlet; car reports the error. Same is true for the UMC, at 120v, the grounded wire has to go to YYY. Nice.