Steve - have a look at my binocular telescope gallery. It shows Paul Shoppis' design that incorporates rotating secondary cages in order to be able to adjust the interocular distance for different observers. I'm basing my design on this one with some material modifications.
http://www.omaroo.com/index.php?opti...g2_itemId=2211
As you can see, the cages are built with an OD slightly smaller than the support platform they sit on, and are held by a simple flange. This flange has a lower bearing surface made of Laminex (akin to the altitude bearings on a Dob) and it rotates on teflon pads attached to the platform interface. This is all held in place by a simple roller bearing whell arrangement as show. Rotating the cage results in almost zero image shift.
Hope that helps....