Sy/dnLcal - I'm not sure it actually tells you anywhere, but you're suposed to leave the GoPro 3M mounts for 12 hours to cure, then they're solid as a rock. I'd be wary of what you stick them to also, anything textured is a PITA. I know a couple of people with them, and they've had them internal/external with no issues.
As for the suction mount, I have a tether