I have managed to get my Madbull adapter working on MWS mags. There is a serious knack to being able to do though. Mag at a certain angle, adapter at a certain angle, more pressure than originally thought etc. now I can fill the mag easily in one go, but it cost me a half cylinder of propane working it out.
The only other question mark is around the metal nozzles, but seeing as all my gas cans have metal nozzles bar the maintenance gas, I am not too bothered about that.