How to modify fiber fenders?

[bugsoup]

It has been reccomended to me to buy instead of mold my own fenders. Suppose I do buy fenders for my project. and I want to widen them, add New Beetle taillights to the rear, and add Porsche 993 headlights in front. I would rather build them to get exactly the shape I am looking for instead of risking ruining a set of perfectly good new fiberglass fenders by hacking them to peices.

My questions: Which would truly be easier to do, mold or modify (assume only fiberglass and no CF at this point)? Should I build them out of steel instead? Does anyone have pictures or procedures for modifying Beetle fenders? I'm interested in general fiberglass techniques, but Beetle fenders should have their own quirks because of the complex curves, so Beetle specific would be best.