I've built several rifles on Mega uppers/lowers, and I have the pleasure of knowing Clint Carrico personally as well. The Mega parts are superb, both dimensionally and in finish-- my only "I wish" is that I could get T-numbers on the uppers, but that's a nit-pick. The tightest rifle I've ever built used Olympic parts on Mega receivers-- I built another for my stepson as a welcome-home-from-Iraq gift, and you should have seen his buddies' eyes when they saw it. "But-- it doesn't
rattle--" As a side note, Mega is a small machine shop with other obligations, and the lowers were kind of scarce this last fall. I hear they're becoming more available now. You really can't go wrong using them for a build.
Clint is a great guy, and a lot of fun-- he's running a side business after his day job, which is quite demanding, but if you're persistent you can get through to him. It's well worth the effort.
ETA: Incidentally, you can occasionally get them without the "Gator" grooves on the front if that bothers you. And "Stinger" was the old, original trade name-- I don't think they've used that name for quite a while now.