I bought a generic 80% forged lower to practice on for my first attempt.

The side plates of the jig fit wonderfully, but the top plates didn't really fit.  They took some persuasion by a rubber mallet, and I also could only get the hex bolts that hold the top plates screwed down on one side (right side of lower when looking from back to front of lower) which makes me thing the lower I was using was just ever so slightly too thick, or the jig is defective (doubt it, but haven't tried w/ my BA billet lower yet to be fair).  Has anyone else run into anything like this?

Also, when I was finally finished, I took the side plates off and noticed a decent amount of speckled aluminum showing.  Anyone had this problem with their lowers, or what are you all doing to protect the lower while in the jig?  I was thinking about putting some painters tape on the sides of the lower to keep it from marring while in the jig.

Any thoughts or stories appreciated ...