My understanding is cycling a paratrooper is very rarely an issue and when it does pop up it's typically because of poor sealing interfaces somewhere in the gas system (tube to gas block, piston to tube, etc) If it does become an issue, you can open up the port in the barrel into the gas block slightly and get a bit more oomph from the extra gas volume. There are videos of a very short barreled SKSs in Cambodia that had zero cycling issues whatsoever:
Of course, someone is always out to do better:
And better still:
On a serious note, make sure you know your federal, state, and local laws. 16.25"+ for length measured with a dowel from the closed bolt face to the muzzle is the best way to be 100% certain you don't run afoul of NFA rules. Also check to make sure that pinned muzzle components satisfy the length requirement like a welded or silver soldered brake would. I'm sure the CFR states something in the gray area of "essentially one piece" or "permanently attached" or something like that, but better safe then sorry before you go that route.