Posting an update to a line of comments that I initiated on this thread's ancestor, as I had promised I would:
I was having some trouble getting the RMS down when building my models. Per recommendations, I made a series of changes:
1. Replaced the existing dovetail plate with a thicker, shorter plate
2. Replaced the existing scope rings with Tak scope rings that were wider
3. Repositioned the whole OTA assembly on the saddle so the scope rings are centered over the dovetail saddle on the mount
4. Added weight to the front of the dovetail plate to offset the rear-weight balance created by item 3.
5. Moved the one wire coming off the OTA from a counterweight bar attachment to running off the rear of the OTA.
6. Increased the height of the tripod to create a wider base.
Of course, I implemented all of these at once, so not exactly the scientific method.
I have a portable setup, and need to break it down and reset it up for every imaging session.
The results have been impressive. From high single digits, my pointing RMS figures are now regularly between 2.8"-4". That is based on running a 25 point model, running the polar alignment routine in the mount, then running a 60 point model (dual axis tracking turned off during the modelling, 3 seconds settling, model creator software, no points deleted). Relatively effortless. Given my image sampling is 3.5" (and even if it was lower!), this is near enough to perfect for my purposes. Polar alignment much better now, also. I stop working on refining it whenever I am under 6 minutes (field rotation not an issue at that level for my purposes (15 mins subs), but last night got to 5.3".
Thanks to everyone for the suggestions.