Hi again.
Unfortunately, no I haven't.But as memory serves all the US early Flying Fortress were of bare metal colour mostly.There were rudders and fins painted only.TLater it is possible these were paited with Olive Drab on upper surfaces and Natural Grey on undersides.These early B-17s that served in RAF were metal finished initially.But later these were painted with RAF camo scheme.I have found some examples of these.I hope these will help you a bit.
As far as being of the C verion airworthy is concerned.To be honest bombers aren't my favourite aircraft but I've read somewhere that the B-17C was equipped with more machine guns, self-sealing fuel tanks, more armor plating, up-rated engines, etc.. than B-17B.Even though all these increased the weight of the "C" model to 49,650 pounds, the installation of the 1,200 Wright Cyclones made the B-17C capable of 320 MPH, the fastest of all B-17 variants. So I think that the variant was a good bomber rather.Of course it was one of whole serie of B-17 and as a one of the first variants had like all aircraft some "child's" problems.