Basically it just gets rid of the on/off in the front of the gun which is right where your hand is when shooting. It's not a matter of IF but WHEN the stock on off will start to leak. The stock on/off is just a bad idea... PERIOD. It's useless and only causes problems and extra maintenence.
Basically, the first thing you should do to a DM6/7 is replace the "airport" with a CP then replace the on off with a CP cap...