I’m not there yet, but I think I’m making some headway. Drilling the holes in the right place is a bear without another CNC or mill.
Get yourself a set of Transfer Punches. They make life a whole lot easier. They are essntially center punches that come in a set of
20-30 different sizes. You just pick the one that fits the existing hole, put it in the hole, whack it, and it puts a center punch mark at the exact center of the hole.
Otherwise, just draw out the part in CAD, take the DXF to a shop with a Water Jet machine, and have him make the plates. They are perfectly accurate, and it only costs $30-50 depending on the size of the plate. And, the holes will be just as accurate as your drawing. I just built a big 4’x4’ machine, using 15 large 3/8" thick plates full of holes. Total cost of all the plates was under $400.
I’ll have to get the center punches. I’ve already bought the plates, but thanks; I can use that resource in the future.
Been there done that…