I've had a stubby stock on my rifle, and an A1 stock... one's too short, one's too long, and neither of them will do after the sunset.  My RRA M4 stock is in route, and I think I saw something about it being hard to install.  Anyone have any directions/suggestions, or is it pretty much as putting on the receiver  extension (proper term, not buffer tube?) for the stubby?

I've never installed a stubby stock so I don't know how they install. I'm assuming they install like the A1 or A2 stocks, just with a shorter tube. First thing first, get a telestock wrench if you don't already have one. You will need it to tighten the buffer tube nut (castle nut?). I have the extra heavy duty telestock wrench. I've found that it works fine on all styles of castle nuts. You should be able to figure the rest out once you start. It's pretty straight forward if you've installed any stock before. There is an extra piece (flat piece) that goes betweent the castle nut and the back of the receiver. Just make sure it's fitting right (flush) into the back of the receiver.

1. Screw the buffer tube into the lower but...(2.)
2. Make sure the flat piece is infront of the castle nut and the "tit" on it is lined up in the buffer tube thread groove and flush against the receiver. (you'll see what I mean) This keeps the tube from turning.
3. Tighten the castle nut with wrench (make sure nut grooves are facing out, or towards buttstock).

add: once you start working on it you'll see that everything will fall into place...sorta like a puzzle.

Before you turn on the castle nut make sure first you havent lost the rear take down pin spring as it will be under pressure and be careful not to mash it with the lock plate as you turn in the extension.Once its rotated in the proper way bring down the plate pushing down the spring and tightetn the nut.I use a little lock tite on the first few threads so it stays on as I dont like to stake on the assembly as the way colt does.