eq6 can carry a 12 inch but not for astro photography, the rated loading on these mounts is 25kgs. considering the ota alone is 22 kgs, and your rings are going to be approximately 2kgs. your right on the boarder line. you add in a digital camera and the OAG scope to guide with, and your well over the rated capacity hence your guiding is up the creek. 12" and over require a mount like the losmundy titan or there abouts to hold its carcass, and in any case a truss is not for mounting its for pure visual. though you can get a goto system and a tracking system for a dob (see servo cat and argo navis) these are not cheap. but in saying that they are cheaper and lighter than a losmundy titian mount
