Ok... so after talking to Kuryakyn, they authorized Wingstuff to send me a new set upon condition I return the old ones.
Fair enough. Going back to box them up, I grabbed one of the non-broken screws and tried just screwing them into the shell pieces while holding them in my hand. Out of 12 screw holes, the screw would only go into 3 of them.
So I was like, "Ok... what the $!#$!"???
Took a really close look and the black coating was so thick that it was encroaching into the screw openings where the threads are.
I don't mean random flakes and chunks that you could get out with a toothpick or by blowing on it, I mean the holes were too small for the screw to go into to even reach the threads. This also speaks rather poorly for the quality of the screws (haha) that just trying to twist them through the black coating snaps the heads off and leaves a chunk down in the threads.
But whatever... I'm getting a new set, and I'm already out the $100+ with shipping, so I'll give them another shot. I definitely won't be using their screws, and I'm not sure what to do if the new set also has the same issue with the black coating.
Get out a sewing needle and a miniature hammer and try to chisel it away? I have a drimel but no attachment remotely small enough to cut it away. These holes are SMALL, so I guess I'll just cross my fingers the new set doesn't have this issue.