Hey Thomas,
I've just been following the thread silently as I'm at just as much of a loss as anyone else regarding a definitive source, but I did have a thought:
Your very tight clutch technique may have worked under the pre-RA-extension configuration, but then the RA extension would have extended the moment arm on your RA axis by a few inches. This small difference in moment arm could be just enough to induce a very slight deformation in the RA axis when the clutches are loaded so heavily. I hypothesize that a reduction in that stress will smooth out your guiding, and that stress reduction could come from lowering your clutch pressure or removing your RA-extension, which it sounds like you already have.
I have had my mount for a couple of years now. I also have the RA extension and I was also noticing that my guiding was getting worse. I tried to tighten down my clutches but just couldn't improve it. I had it down to .25-.45 arcsec about a year ago and it just started creeping up to over 1 arcsec even when the seeing wasn't that bad. I tried worm adjustments, clean and relube, clutch pad replacement with Michael Herman's pads; just about everything.
Ultimately, on this forum I came across the advice to have the clutches barely tightened so the mount could easily be pushed if needed. I carefully rebalanced (rolling DEC to 0 degrees) and marked my mounting plate with my saddle so I could easily repeat the position. I tried barely tightening to contact, polar aligned and, hit "Play" in the NINA Advanced Sequencer.
Currently watching the mount settle at .3-.7 arcsec again with none of those severe sawtooth RA excursions like I saw before.
I'm sold on Chip's "barely make contact" with clutch technique.
Also, when I took my axes apart to clean and relube I noticed some wear on the shaft where it touches the needle bearings. I am pretty sure I induced this by over tightening my clutch over time.
?
I can imagine your frustration right now; I bet we have all been there at some time in this hobby, and I hope the RA extension removal gives you some instant satisfaction so you can get some imaging in. But I would encourage you to not give up on the RA extension and give it another shot once you feel like you aren't chasing ghosts in the mount.
Wishing you clear skies and a rewarding imaging session,
Ryan
Ryan Noonan