Quoted: I am cutting down my own barrel. Anyone know what the gas port sizes run with the approximated barrel lengths of 7.5, 10, 11.5, 14.5, and 16 inches. I have not decided if I'm going pistol or carbine yet. Thanks, Rick

Staying with a rifle length gas system, the absolute shortest I would go is 16.5", 17" being much better.
There is so little barrel in front of the port that you obviously have to open the port WAY up.
Rifles setup this way can be finicky about what loads they like to run.
More barrel length out in front of the gas port goes a long way towards accepting a wider range of ammo.
I have a drawing here of all the gas system lengths an AR-15 barrel can be built with.

I once had a guy bring me a barrel that was cut to 15.5" and it could NOT be made to function even with a 0.120" gas port.
Relocating to a carbine port fixed it.

Now, with the Carbine length gas system, the absolute shortest you should go is 11"
Yes there are some 10.5" that work, but it's not optimum, just like a 16" dissipator is not optimum.
If you want a 10" or shorter, the pistol length gas system is MUCH better.
The gas ports get mighty small on the short gas systems!