I did something like that on a power boat to close up two large holes in the liner (8" X 32"). If the compound curve is not too extreme, use a piece of 1/32" gloss finish laminate (formica)cut oversize for a form .Taper everything well on the inside of the hull, then use contact cement to temp glue the Mica around the perimeter of the hole on the outside surface of the hull(or if the compound curve is too great take a mold off the good hull) and build up everything from the inside. After the repair you can break the bond of the contact cement with laquer thinner, wipe it clean with out a trace. Of course you have to have release wax where the actual repair lays against the form. Worked extremely well for me.