i've used the rc4 system before and actually liked it.
just curious...did you hold the release switch in all the way, while pulling on the lever? there's a secondary safety on the rc4. if you just push the switch and pull the lever, about half way, you'll have to push the switch again to free it completely. i'm sure you know this but i've had to show a couple people how it worked in the past.

), but my major complaint is that the rubber on the plate has very little friction to it - its just too soft. Even when a tripod collar/camerabase or focusing rail is screwed on very firmly there can be slippage to the sides if the setup happens to lean one way or the other. I've even had the glue on the rubber slip the rubber a little and it push out of its mount (not by far, but a little bit). So the Arca swiss was interesting to consider for its more sturdy (from what I hear) grip to the camera/collar/rail.
