So, I now have two different sets. I have some metal STG-58 ones and some plastic penguin ones. Both are nice. I'm partial to the feel of the metal ones but I do see where the plastic ones might be a bit more functional.
Perhaps if I want a little winter project I will pick up a set of the Magpul MOE rifle handguards and see if I can make them fit.
With enough work almost anything can be made to fit.