ok, just did as you said and the base plate does move. takes a fair bit of sucking to move but an engine should be fine with that.
yeah the dead spot kills the engine so the revs do drop quite dramatically. if i dont blip the throttle it will just stall. so i guess it is fairly logical. the annoying thing is that once the revs are above the dead spot it accelerates fast and easy regardless of how quick i push the pedal. as far as i can see everything is functioning and its more than a little exasperating.
by the way i reset the plugs to 0.8mm first thing.