Hi
I've only removed Mylar once from an em gtb, used hairdryer method and had minimal paint loss. Cleaning up the residue was the hardest part, took hours with shellite and a Ton of rags.
I have heard good reports of putting playfield in sun for a few hours to heat whole area first, I will be giving this a go on my Gorgar when I get to it. Another couple of thoughts I have on this is to pull Mylar from top to bottom or visa versa, as opposed to side to side against the grain/planking, also pull Mylar back onto itself as opposed to pulling in a upward motion, this I feel would reduce the chances of paint lift. Anyways these are my untried thoughts on the matter, good luck with whatever you decide. Gav's method sounds good and would be worth a try first.
Cheers
Dave