I just measured up my McCoy 049, thinking that whatever the mounting dimensions are, they'd round to some easy fraction of an inch.
I was wrong: it looks like the radial mounts are on an equilateral triangle, 0.837 inches (+/- 0.005 at least) on a side. This doesn't seem to round out to anything sensible.
So -- anyone know for sure? I'm really not good at measuring hole centers, as I find out whenever I finish drilling something up and go to try to bolt it onto something else.