This video show how Ron Paulk runs CarrySpeed & L Bracket
Ron Paulk's take on the Carry Speed FS-Pro Camera Sling
Thanks for posting, I think it is on their blog, right?
It confirmed what I thought, it is not designed to work with L-brackets, or any other plates one might be using already. For me a show stopper, for others who don't use QR plates yet it might be less of an issue. Drilling a threaded hole into an L-bracket as a workaround seems to cumbersome for me personally, especially when there is a flexible solution available (Blackrapid or any oher strap with a screw-in lug attached to a QR clamp):