Wooden mudguards

Yeah, they'd come out with a little flex in 'em for sure, though they'd have a pretty strong "memory" to their first position, so if you wanted them hold at a different radius you'd need to support them there with mountings.

I'll start doing some research see if I can knock something up

The compound curve would be possible, but tricky. I'd have to build up a larger mudguard blank out of stripwood laminated round a form, then shape it to the final profile with a spokeshave.

RE: using old rims for a form. Wouldn't I want the radius slightly larger than the wheel (EG use 27" rims for a 700c wheel) to allow the gaps to be even when it's set back from the tire.

see....once you start talking about compound curves and such like i end up being a second rate mechanic