To avoid hijacking White Rabbit's thread I have started a new one.
Hey Iceman, if you are having trouble obtaining a set of tube rings for your 12" GSO OTA, something like this might do.
It's only 6 pieces of 19mm plywood and 4 clamps (or 2 clamps and a heavy duty hinge).
The one in the attached photos is one I made for a 12.5" F6 OTA I have in the workshop at present. Only took an hour or so to measure/cut/glue and screw. Just take the altitude trunions off, attach a dovetail and you are away. It is quite rigid and should be OK for imaging.
Once I finish star testing the 12.5" mirror (soon I hope) you can have the cradle for the cost of the shipping (shipping might cost a bit as it is quite large and heavy). Only trouble is the cradle rings are cut for a 390mm OD tube which is probably way too big for your tube.
