After marking out the rectangular hole in -03, I drilled it out using my hand drill and many 3/32 holes leaving the roughed edge in picture 1. I used a rat tail file and a flat file to smooth the edges, then debured (deburing tool and scotch pad) leaving picture 3. This took a lot of tedious time, but I could bot think of a better/faster way using the tools I have.
Pictures 2 and 3 show the splice plate attached with clecos.
