Dave: Make a pattern, first. Use heavy craft paper, sort of like the material used to make shoe boxes. Cut it out to fit the flat area(s) where the gauges and switches will mount. You can then lay out the gauges, spacing them evenly. Find the centers for each, indicate the centers on the pattern, then tape the pattern over the panel where you'll transfer the centers to the actual panel using a small drill. Drill pilot holes for the correct hole saw(s), then cut out the holes. Note: Always error on the small size. Using a sanding drum on your drill motor, die grinder or Dremel tool, open up and smooth the holes for the final fit. Use the gauges and switches during the fitting process.