Thanks, I didn't know about those little circle cutters---I've been assuming that without metal-shop tools we couldn't cut metal lensboards in reasonable safety. (Wood is easy, but wouldn't hold up to being cut as thin as the little rolled lip on a Pacemaker boards.) I don't know why it didn't occur to me that the release arm was removable!

I think mostly I just needed to vent after a frustrating succession of "looks like it should work but it doesn't" moments.