If anybody buys a Zumo 660 and has a Techmount which they've previously had a Zumo 550 attached to they will need one of these as I recently discovered. £13.00 from Bykebitz
(http://i151.photobucket.com/albums/s139/Jaffa_Cake101/Fingers/image-3_zps40098016.jpg)
You can cut the original plate down but this is a tidier option.