The Manfrotto RC2 QR system can be used one handed - just checked with both hands to make sure! The clip locks open when fully opened and is released when the QR plate presses down on the release pin. A bit of a fiddle BUT it was the first time I've tried and I'm sure that practice would improve my technique. I would put a 1" or so spacer between the camera body and the QR plate to make it possible to operate the release lever while having control over the camera - when I tried it, it was with a spotting scope on an L bracket. I would also stick the strap round my neck during mounting/demounting, just in case s*** happened!