I would like to install a single piece tub/shower surround in my downstairs bathroom. I have two doors to go through. Both are 31". The tub surround says it is 30" but with a 1 1/4" nailing flange that puts it at 31 1/4. Can I trim the flange down by 1/2" without hurting the surround so that it will fit through the doors? What should I use to cut the fiberglass?

I would remove the doors and part of the door frame before I'd trim the shower surround.

Definitely don't trim the surround I would dismantle a house full of doors before I tried cutting a fiberglass surround. GOOD LUCK, AC

You will be better off dismantling doorways. You could very easily damage shower by trimming flange.

It can be done, but it is definitely not recommended. You would probably find that trimming flange wouldn't get the shower though the door and then you wouldn't be able to return shower because it had been modified.