So, I finally got my lower build kit from PSA today. Managed to get it together with only a small scratch on the bolt catch area. I'll touch that up with some paint later. Surprisingly, the pivot pin detent didn't give me any trouble at all and I didn't launch any springs across the room!
This is the first time I've built one with a carbine stock, and I think the Magpul STR will work well. However, I think I need to get myself a stock wrench to get the castle nut on there tight enough. The buffer tube was still wobbling a bit with as tight as I could get it by hand. Any suggestions for a good AR wrench and/or multitool?