And what or why are you thinking of the Arca?
the Arca system is the QD base system the head uses. the nice thing about it is that it's an industry standard, so you can mix and match clamps, QDs, plates etc and they will all fit. I'm going to machine a CS base with the reverse dovetail integral to it, which is one less part to align, one less fastener, one less tapped hole etc.
http://warga.ca/ForumPostImages/Arca-Mounting-Plate-Dimensions-Diagram.gif