I just used a pair of tinsnips either left or right depending on how you are orentated To cut the scallops Its compleatly under control and no chance of the sanding drum making a big gouge. Time is not really a factor I think it took me about 1/2 hour to cut both of them. Probably about the same as it would take with the drum sander.
I wish I was working now on my plane but instead I'm killing time in Portland (100miles away) getting radiation treatment for prostrate cancer. All part of the price for answering the call of duty and serving in the Air Force in Vietnam. The duty that keeps on taking.