The only real thing I see with that (the original question) is that the prop and spinner may not be exactly square with the cowl. I don't think that's gonna happen no matter what you do if you maintain that thrust angle, or do I have a misunderstanding of the problem?

I have two cowled planes, and both of them have the cowl that is not exactly square with the cowl and that's because the cowl is square with the plane but because of the thrust angle of the engine, it cannot be square with the cowl.

Please correct me if I am wrong because I am putting together a Seagull Super Star and it has a rather large cowl and I want this to not only perform well, but to look good too.

DS.