WAAAY back in the day when there was only gunsnet, someone restricted their gas port by tapping it for carbeurator jets and swapping out different sizes. Never ever heard how that worked out. You could do that plug thing, which would keep the gas going down the barrel.
If on the other hand you feel it would be OK to have it always "under-powered" by venting the extra gas, then it would be easiest to simply vent the "extra" gas at the tube.
If the screw/plug thingy works for biggun's .223 ? pressures then it would certainly work for the lower pressures of the winmag