Some recent eBay auctions have turned up various proofs from this set, which seems to be the easiest way to find anything as I still have yet to see an assembled one. Two of the proofs I've already posted about but two are new and the auction description also has an interesting tidbit.
Here is a proof of the Bell X-1 fighter:
The second proof gives the Skyray F-4D:
I'm not sure what those punched holes are for but some proofs have them and some don't. The holes had some significance as they are cleared on the back of the piece against a backing board, so maybe they were to hold them in place for some reason.
That wrapper is just leaned up against the back, it's not attached. 25% of the set has now been documented in proof form. That's pretty good for something this obscure I think but it's weird proofs are found more readily than the product they were used to create!