Trimmy, trimmy, all OK. Even the dodgy props did their job nicely.
Have a trial sit, and am stunned to discover my shoulders do not touch the shoulder rests! They make a lovely elbow rest for entry/exit though, considerably easing the process.
Drill out the center of the hardpoints to 1/4". Make a drill guide to hit the absolute center of the hardpoint, and it delivers a result that is not at the absolute center. Do the others by eyeball and they look better.
Cut some 3/4" wide bits of carbon fibre test bits I have lying around, and rivet on some 1/4" nutplates. Cut slots with multitool and dremel router bit and trial placing them.
Contemplate stupid drill guide for a while, then fling it across the shed