major surgery for minor gain in space now seems rather pointless taking into consideration everything that's been said - until I've at least paddled the boat and can decide if an inch or two here and there is really going to help

this certainly makes the most sense as it will give you a benchmark to react from after using. But making cockpit modifications is an easy change that I have done many times and the few inches or fractions gained here and there can make radical (really) differences in a the boat's cockpit ergonomics. Do not be afraid to change it if it doesn't feel right, but use it enough initially to be sure of the change desired.

Looking more carefully at the resolute and chesapeake, the sheer hts at the ckpt are quite different - I estimate the chesapeake17 std is in the range of 1 1/2 inches higher at the ckpt, so the side footrooms are going to be different.

Also there is one more unusual ckpt game you can play . . . you can cut the ckpt perimeter another inch or much more wider radially all around, but build a wide coaming rim such that the new upstand location lands somewhere in the middle of the rim. Pad the underside of the rim with foam all around and just cutaway the regions that you need more thighroom. This approach can also be made more locally while still keeping outer perimeter coaming curvature for the now larger sprayskirt that you will have to buy, make, or modify (it's just glue depending on the rand). You can see something similar in many builds where 3/4inch wide or more upstands are built all around the ckpt cutout to attach the rim to. If you have this, maybe also grab the rasp and hack away some ply layers - locally you only need 1/8" or less if covered in glass.

Anyway, some ideas.