Triming Exterior Fiberglass Door

What's the best way to trim about a "1/2 of the top of a fiberglass door? Would a plywood saw blade work or maybe a jigsaw? Thanks.

Tape to prevent splintering, straightedge with clamps, circular saw with sharp, fine-toothed blade. Be careful, 1/2" may require you to glue in a new wood piece between the fiberglass skin. Drill a small hole to check the thickness if you are not sure.