Yes, sadly, given that the real thing in steel had only marginal operating power with the recoil of a .455" Webley cartridge, I have a feeling that any attempt to copy it in light alloy in CO2 form would not function - unless it got about 6 shots per 12g CO2 cylinder. I mean the Umarex DE has a very light slide and turns a small light cylinder when it cycles, but runs out of gas after around 25 shots (and is NOISY).
You might be able to make it work OK with a 95% plastic upper, but who would want a 50% plastic Fosbery?
Well, maybe me. If it worked. But not many others.