Haven't tried this - and it's a tad pricey - but it is another option (The Box):

http://www.16x9inc.com/cgibin/eDatCa...ogno=BE-BOX-FS

Solution for JVC HD cams w/IDX or AB battery
 

These pictures are from an Aussie website (provis.com.au) I will post better pics of my rig soon.
It is a bit heavy but puts the Firestore on the correct side of the camera.

The BEC Group also make mounts for the Firestore units (see http://www.thebecgroup.com ). I have one of their brackets that mount to the Anton/Bauer accessory plates.