Hi Pete. Yeah, I should actually have the fender off in the next week doing some work. I'll make measurements then.
Honestly, If you're looking at using any kind of hard bag, you don't need measurements. The bracket simply uses 'J' hooks over the sub frame as you can see from the original thread. Then at the point it becomes exposed from beneath the fender, it bends out to be even with the fender. From there you just measure your holes and drill through whatever bags you've purchased.