I've looked through this forum and seen numerous threads regarding hand guards, but nothing on mono-uppers, so hopefully someone can help me out.

I'm amassing parts for a build and I decided to go down the piston path. I picked up an AA XLP kit and now I'm looking for monolithic upper that'll clear the low-profile gas block and come with a barrel nut that will play nice with the rod. My original plan for this build (before I decided to go piston) was to use an Aero Precision COP M4 upper and I was happy to learn that it plays nicely with an AA conversion kit, but after looking further it appears that it works with the "standard" gas block ahead of the rail but no info on whether it works with the low-pro gas block underneath the rail. Can anyone confirm this set up will work?

Are there any other mono-upper options that are known to work that anyone would recommend? I'd like a longer fore end than the Aero, maybe even rifle-length. For reference, I'm using a 16" barrel drilled for carbine-length gas system. I'd prefer to only have ~2" (4" with muzzle device) of barrel exposed.

Thanks!