Looking for AR pistol advice (assembly in progress)

[Proximal]

As said above, a buffer tube on a pistol is fine, as long as you dont attempt to fix a stock on it. The law states that it cant "readily accept a shoulder stock" so wrapping the tube in tape or parachord or dipping it in rubber are all acceptable solutions. or, just use it as-is. Lots of people do.

As far as barrel length and tubes go, as long as you stay with a specific configuration you are good. Rifle tube with rifle buffer, carbine tube with carbine buffer, etc. Depending on the gas port size and dwell you may need to adjust the weight of the buffer later, but usually a standard or H1 buffer will be OK.

Awesome! I'm about to order a CAR length buffer tube assembly. This seems to fit the bill for a 12.75" upper based on similar length models (Colt commando and M4).

That's what I'm planning...paracord that badboy. I had a WASR several years ago with a Romanian wire side folding stock on it and paracorded it..made it much more pleasant to fire in cold weather, lol.

I'm in total agreement. This sounds like a good way to go.