I ground the excess material off the edges of a leading edge fairing for trial fit, but unfortunatley it won't do. There are too many gaps in places I can't fix without lots of flox or other filler, so I'll fit the rear fairing and match-mould the leading edge to overlap instead - reverse of the way they're manufactured (changed for the Evo I believe). I wouldn't want to have to re-make the aft fairings - they're a pretty complicated shape to encompass the inboard end of the flaps!
Once the decision was made it was just a matter of taping up the wings to support the moulding wax.