Decide on a novel approach. I will cut the outer skin, and shape the internal foam and judiciously cut the inner skin until my carved form fits into the hole, then contemplate the result. The aim is to just glass over the result and I'll have most of a NACA duct.
Cut the outer skin with the multitool, rough shaped with dremel 1/2" sanding drum, finished with square file and sanding sticks. Cut flox corners for the inner and outer skin, then repeated on the other side.
Spend much time contemplating result, and plotting next steps.
Two conclusions:
#1 Grant picked a nice spot to sign his name on the inside.
