Does a volume fix exist for this version? I have the red pcb one, and all the C11 mods say that it only works with the green pcb. Does a similar easy fix exist that stops the irritating volume loss?

In short? No. However...

The volume loss mod has an effect on the fuzz sound apparently - from what I've heard, you lose the gating effect of the fuzz. Or some other characteristic changes.

If I ever get a Blue Box, I'm going to put a boost in front of it, and have those two pedals running through a looper pedal so I can switch both on and off with one click.
Apparently the change in fuzz makes it more trebley, kinda what im looking for, but thats only on the green pcb.

At the moment im running it before a GFS Black Hammer distortion and it works out...ok...i guess..for songs where I only need fuzz because i can scoop the gain and tone on the BH, and max the volume so its just a boost...but id prefer the fuzz to have no colouration, because there are songs where i need the distortion to...well..distort, and the fuzz to fuzz.