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Hi,
I concur with your observations of the G11 when used with anything bigger than a refractor.
I started AP with a G11 (60 lbs capacity) and spent a few years tuning, and tuning, and tuning. It was OK and I could get useful data from it, but not all the time, it sometimes would 'flare up' and give funny star shapes. Now mind you I was using a C11 at f/10 most of the time, so I was pushing the limit, but the gear box noise problem (76sec quasi-periodic spike) and somewhat random nature of the PE made it frustrating to use in an observatory setting. I believe the simplicity of the worm mounting scheme is the root cause. The components, brass, steel, aluminium and plastic (gearbox) all have different coefficients of thermal expansion and just don't sit where you last left everything after tuning/adjusting, also the rigidity of the mounting is suspect IMO when doing portable.
So I upgraded to a PME (140 lbs capacity), HUGE difference. It handled the C11 with spectroscope + a C14 with long imaging train side-by-side. I could start a session and pretty much guarantee guiding would work, no fussing around. The worm in this case is spring loaded, temperature changes did not seem to have much effect, the PE was reproducible, no fast spikes from gear boxes etc.
Then I changed the scope to a CDK20, used it for a couple years and succumbed, it was a bit too much scope for the PME, so I upgraded to a Planewave A200HR (with encoders), again HUGE difference (240 lbs capacity). What is nice about the encoders is that mechanical PE does not matter anymore. The encoders do PE/gear noise/belt slack/whatever correction in real time on the output shaft.
The pointing accuracy of the encoder mount is extremely good but really unnecessary these days with modern plate solving. Especially since when I rotate the camera (motorised IRF90) there is an offset that basically swamps the pointing accuracy, but again don't care with plate solving and ACP.
I understand the cost bump is pretty big so take your time and really evaluate what you want to do, the G11 can still do a lot.
EB
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