G'Day g_day,
I would agree with your assessment of the CG-5 dovetail. I had similar problems and like you I went to a motorised focusser, but I still notice unacceptable movement in the wind. I expect the CGE dovetail is probably significantly stiffer.
I don't think the size or number of the screws attaching the dovetail to the OTA is a concern. They should be plenty strong enough.
Apart from the alternate dovetail and rings solution, and alternative you might like to try is to make a new solid dovetail bar to replace the CG-5 bar.
I suspect the grooves in the bottom of the CG-5 dovetail bar seriously diminish the bar's polar moment of inertia and allow it to twist easily between the mount and each end. I haven't got my act together to try that step yet
.
Al.