thinking about going with Magpul XTM FDE rail covers for the 15-22. How many 4 piece packs will I need to cover the 3,6 and 9 rails completely?

The sides need 6 panels, and the bottom needs 4-5, so you'd need four 4-packs, or 16 panels.

I'm using 4 on the bottom rail, but I'm also using a vertical grip.

Thanks Rusty. I'm also gonna try to run a BAD lever and MOE grip. Haven't decided on sights yet. I'm thinking of just using a T-1 and no buis. Too bad the ASAP plate is a no/go on the 15-22

Being a lefty I don't have a need for the BAD lever.

There are other ways to get a sling loop at the front of the tube. Midwest Industries makes a few different devices that may be adaptable to the 15-22. Midwest Industries: End Plate Sling Adapters

I really like the MOE grip. The fatter profile fits my hand better and the flare for the web of the hand give you a good reference for a consistent grip. I really wish the MOE+ would come out (rubber coated revision), but I am a big fan of rubber grips.

T-1 clone from Primary Arms is a good choice. I think a 2 MOA dot would be just as accurate as iron sights on a rifle like the 15-22. The 4 MOA works great inside 50 yards for me, but at 50+ I like to use irons, and I'm probably going to a thinner front post when I get around to shooting more.