How are you going to hinge it?   With cloth hinges I round both surface edges.  With the pinned nylon hinges I make a vee shape.  Might try a search for doing nylon hinges.   

Bill Sawyer (Windancer Models) makes one for the Bill Simons sized P-39.

 Doc I'm usng nylon hinges The model is a Walter Pyron design. I attached a pdf of plan. I'm not that good at carving which is why I've been hesitant to mold canopy.

HI John,

IIRC, you can make a Sig 9" WWII canopy work by moving it around and cutting it with some "imagination".  Since Bill Sawyer is gone, I don't know of another source.  If Walter Umland has any "extras" for his kit, one of those could probably be cut to fit.  Different airplane, but close enough in size to make adjustements I think.

The design was republished in the FM Classic Series.  I have those plans (somewhere) and if I can find them I will relay what was called out on the plans for it.  Exact same design, just some updated construction, etc..

Big Bear