Thats really interesting - you seem to have found something there. I know for a fact that as soon as i tightened my turn i saw an immediate improvement in the conistency of my striking. That seems to be what you are describing so thats good news and that handicap will soon come down.

As to the weight shift, yes you can transfer too much. Its actually a lot less than many people think, especially with your irons. I am not going to get into % but here is my tip which i use to diagnose weight shift problems. If my finish does not see me straight on my front leg (ie i am reverse c'ing) then i am not transferring my weight correctly. Either i am turning to much (like you were) or not enough. So i know if i am transferring correctly on the backswing by looking at the follow through.

I never think of weight shift unless i am having problems with striking and follow through. To solve problems i make sure a) that my back leg remains bent as it was at address and b) that i am turning my shoulders behind the ball and really coiling into the backleg. Do that correctly and the downswing just happens.

I hope the above is clear enough. It seems like you have made a breakthrough IMO. let me know how you get on with it

nick