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Thanks for all you replies guys. Yeah I was aware that I would have to use a flattener with the GSO, I read somewhere that over about 24mm image circle it was really needed. My current thinking is that on day one I have my Meade with a 0.63 reducer/ flattener. At least I will be able to use the same area as my ST2000 and probably a bit more before I have to start throwing away pixels that are to bad either from vignetting or coma etc. I also have a 5yo WO Megrez 80mm F6 APO triplet and a Televue 0.8 flattener, that I think probably will have a biggish corrected FOV. So I am then looking at my next move.
Looks like I may be a bit constrained by my G11 as to the max size scope I can carry and still expect very good guiding etc. I have tried out an 8" GSO RC on this mount and it is so light it handles it with ease. It gives EXACTLY the same results in terms of resolution and image scale as my Meade 10" OTA at F6.3 with reducer. The only measurable or visible difference was a 20% drop in peak brightness of the stars on the 8". The 8" should have been worse but it had several things going for it. No corrector plate or focal reducer and higher quality in the reflectivity of the new coatings. Both ran at 1600mm and I could not tell the images apart visually by flicking between them and only just using measurements. The FWHM was identical for example. In a blind test my friend could not tell me which one was which.
I wanted to get a sense of the improvement I may get from going from an 8" RC (the benchmark being so much like my current setup) to either the 10" or 12" GSO RC.
Adding the STL-11000 adds extra complication due to it's large field. I don't know if combo focal reducer & flattener for these scopes exist to mitigate the extra focal length making tracking etc harder. However I don't have any tracking error issues now so an extra 400mm or so shouldn't be to much worse.
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