Hi Wolfy,Thomas at edge offered me a real good price on a big bore kit while I was playing around with turbo's I never took him up so have no real world experience. But only the other day I was talking to someone about them and he said that the edge pistons were rumoured to be to short in the piston skirt allowing excessive movement in the bore and causing some problems. I can't remember whether he said it was already fixed or not.
I can't verify whether it is true or not.
Another option is rotax performance Australia, Steve would sort you out.