thanks for the reply mate. much appreciated.
the trouble is , having looked at you pics, the extreme is slightly different than the jnr version which i have. for some stupid reason the hole where you have fitted your Q/D for the remote is quite a lot (about 3/4 inch give or take) further forward on my gun, meaning if i look up it without the plug installed and a 12g in place, i can see the shoulder of the 12g. this means that any air fitting i put here would feed in front of the valve, pressurising the whole 12g compartment (not a cut away drop changer like yours) instead of into the valve like yours. seems pointless to me! would put up some pics but ,like everything i own, my camera phone wont work.