I'm currently working on a project of making a CF roof skin as a replacement to the original. The original will be cut out leaving a flange around the edge and the CF one will be bonded to this flange.

what car is this for? does the car have a seperate centre roof skin ie: with a roof moulding along each edge to cover the join? if so i would take a mould direct from the roof, then drill off the original roof and replace with the cf one. i wouldn't mess around with wax sheet on such a large area.

we curently have a couple of m3's in at work which have cf roofs on them and they do flex a little when pressed, these are bonded directly to the shell and the two mouldings fitted along the sides to cover the join. bmw do have a special glue they use to bond the cf roof to the car along with some fancy clamps made just for the job.

i was thinking of using a layering it:- cf,foam core,cf and at the edges an extra 3 layers of cf tape, not sure if that would be sufficient.