I need to make a total of 44 rectangular holes in some reasonably thin
aluminum. 22 of them have to be .56" x .52"; 22 have to be .81" x .52"

I had assumed I would be able to go down to harbor freight and buy a
rectangular chassis punch; no, the cheap generic punches are all round,
and the only rectangular punches I've seen are special-order for
hundreds of dollars.

So... any good ideas (or sources of cheap rectangular punches!), or
should I plan on a day or so with my nibbler and a corner punch?
--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)