[knomadd]

I personally like using some sort of inner fender. It helps keep the road grime and trash out of the engine bay. Even if you rarely drive it, they will help keep the dust down to a minimum. So my vote would be to trim them and modify as necessary. Fiberglass isn't so difficult that I'd recommend tossing them. I'm sure you know this, but before you start trimming be sure to wear protection for your skin and lungs!

But note that I've never worked with turbos, so I don't know how the heat they produce will effect the fiberglass, or if it will even be an issue. Good luck, and have fun!