@DrC thanks for the suggestions. Believe it or not the 85 does stick out below the bottom of a T2i! However, for my purposes the T2i's frame is nowhere near rigid enough even if I could bolt it down sufficiently. I need to have less than 1 pixel's displacement over a series of 1000 captures or so. The trouble is the mirror slap. I know how to lock it up and then shoot a picture but I'd love to leave it up and locked out of the way. Anyways, 1 pixel of motion is about 40 micron at 3 feet away (gotta love mixed units - at a meter away) which is about 8 arcseconds of displacement. The Manfrotto support you listed is for-sale on Amazon for ~$70 and is similar enough to what I'd have built that I'll save myself the time. Tha