how did you cut out foam?

[BigLew]

Depending on how big a piece you want to cut out at a time, you might want to use a buck saw blade. (The kind that is mounted on a steel frame similar to a hacksaw and is used for limbing out a tree or cutting firewood when you don't have a chainsaw available.) Make sure you make some sort of handale to protect your hand. Cutting a paint stirer in half and riveting that to the sides of the blade is one idea that comes to mind. To cut the blade, you could use a grinder I am sure and to pop rivet it and drill holes I'd would you use a stone of some sort that would normally be used in a dremel tool. You could mount that in the standard electric drill for what you're going to be doing. I don't think the standard drill bit will easily drill through that blade.

To use it, just work it under the foam and start the sawing motion, keeping the blade flat against the fiberglass and your hand end up just a bit for clearance. The blade will flex enough to allow this.

Just a thought. Good luck.