Update on my 09 TE610. Adjusted rear preload for 4" of sag. Increased rear rebound damping (16 clicks out). Bike noticeably more stable. Ran up to 75 mph+. Do notice headshake when behind another vehicle at those speeds. So some improvement, but more work to be done. Steering damper might be in order, but I want to get the bike setup well before I do that.
I read on the TT thread where people commented on the grip of the bars causing the headshake. Something isn't right when grip is causing headshake. I don't think the 610 shock has the greatest compression or rebound adjustment. At least my SM610 doesn't. I have the high speed compression backed all the way out because I think the damping is harsh. I only seem to use the low speed compression. I think I am at around 10 or 11 clicks out for the rear rebound. I think you can still add more rear rebound before you get to an obscene setting. I don't think it is a preload setting either, but your adjustment is seems good. I'd only make one setting change at a time. It's easy to get confused if you don't, and not notice the effect of the change.
Another thing to consider is tire balance? I've had Dunlops give me head shake at the track and Pirellis ran smooth as silk with the same setting. The Dunlops were balanced, but I think the heavy carcass of the Dunlop rear tire just caused the shock to oscillate more.
