), so I'm going to make the panel as attractive as possible; where there are no instruments currently installed, no holes will be cut. Where there are adapters, holes will be cut to fit existing instruments. I will also modify the shape slightly to cover the gaps on the ends (the worst one is on the left, obstructed from view by the hand held radio). Since the cover won't be used, I'll omit its mounting holes. If some future owner ever decides to strictly original, this panel can be cut down and holes added to exactly match the original.I've started with a clean sheet, literally. I laid the old sub-panel on a new 2' x 4' sheet of 0.125 2024-T3 and traced its outline with a blue Sharpie:
I had originally thought about using my AI's instrument hole punches, but they would have required some way to locate the hole centers and drill a 5/8" hole for the bolt, so I just killed two birds with one stone and went with a hole saw. For location accuracy, I first drilled and clecoed the 3/16" mounting holes around the perimeter to securely hold the old panel in place on the new sheet. Home Depot happened to have a 3-1/8 saw that fit the arbor I already have. The size of the saw is accurate enough that it only wore of SOME of the paint inside the holes in the old panel. The recommended cutting speed for the 3-1/8" saw on aluminum is 165 rpm, but my drill press only goes down to 200. A little Boelube on the teeth, and a LOT of noise, and the holes came out nice enough that you have to look close to tell they aren't punched.
Extra-credit question: What other size instrument hole(s) will I have to cut, and for what instrument(s)?
I had to use a coarse round file to hog out the oil pressure and temperature gauge holes out by about 0.010. It wasn't a huge amount of effort, so no harm, no foul. 
