Yes last time we mentioned the Enfield decompressor with copper pipe and probably with a flare fitting would be best.
Just with the remote decomp pipe you may loose 10 psi as this will add to the combustion camber volume.
With the OHV head there isn't a lot of room with the muffler on one side and the carby on the other ,then with ports and valves in the way ,you may have enough room if you drill a hole on an angle so the bottom of the hole is close to the spark plug thread then the top of the hole is at a distance to not get in the way of using a tube socket to get the plug in and out and as long as it's not in the way of the spark plug lead and cap.
