My bike destroys tails lights, rear fenders, ignition switches, and sissybars. This is after getting everything tuned and the carbs in sync. Anything over 65 is pretty ruff on the rear of the bike. I don't feel too bad even with my minimal seat. My vision doesn't start getting blurry until around 75MPH.
I'm having the stretch reduced on my rear right now. I think it had to have been 6" or more. I'm taking it down to 3". And I also have a new rear 5.00 x 16 tire going on. I'm going to fill the rear triangle with the BB+Silicon mix to add weight. It probably won't even be close to stock weight. (~450 lb)
Next (probably year unless I get rich) I'm going to do the Re-Phase and 5th gear.
PS, I commute 100 miles a day down i80 on this bike)