I found another way to mount the C-5 OTA to the Losmandy plate, without having to turn the scope upside-down and use the accessory rail. Both Parallax and Orion sell 5.5" ID tube rings, so I bought the $40 Orion pair instead of the $160 Parallax pair. They will bolt-up nicely to the short Losmandy dovetail plate, and I can still use the accessory rail for mounting other things. I added an aftermarket dovetail, as previously mentioned, and now have my choice of several different Orion finders in place of the stock 8 x 20mm "golf scope" finder. Cute, but not very practical. Actually, that's not fair. If used on a GoTo mount, any small finder is sufficient, even a red-dot reflex sight. Another possible configuration is the C-5 mounted piggyback on the 6" f/8 Newtonian, giving me the option of using either as a "super guide scope", or just tandem scopes for public star parties, allowing two people to have similar views at the same time.