OC-1 cockpit, want to replace existing access port with a larger one.

Existing: https://photos.google.com/share/AF1Q...QzSWJaRW5TYzBR

Larger: https://photos.google.com/share/AF1Q...QzSWJaRW5TYzBR

This might seem like an inane post, but the consequences of error are fairly severe - as in a power tool catching on the material and spinning off into fiberglass that is not to be cut.

There is insufficient room for either a reciprocating saw or a jig saw.

I am thinking Dremel tool with a sanding head - applied so that, if it catches, it wants to spin away from the material instead of in to it.

That, plus time, patience, and care....

Does anybody have a better idea?