On my 04 SEEG with the stock Dunlop tires, tour pack loaded down or no tour pack and a light bike..I had no problems what so ever.
Changed tires to a 18x4.25 rear with a 150 or a 160 tire....front 21x3.5 with a 120 tire, the problem with rear steer is horrible even going in a straight line.
Installed the Sta-Bo bushings and it took care of most of the problem in a straight line, but it is still there.
Re-installed the stock tires and there is a small amount of vibration in the floor boards. The bushings have been in for over 10,000 miles.
Re-installed the 18-21 set up and installed a new Alloy Art stabilizer. ALLIGNED THE DRIVETRAIN, Rode the bike yesterday for only 50 miles a nd the straight line rear steer was not there.
Will not get a chance to put many more miles on the scoot till we get to Daytona, and when I get back I will give more feedback.
From what I have experienced so far, I believe that the change in geometry of the bike with the different tire combinations is a huge contributing factor in rear steer. I am also curious as to how many are having this problem with just a change in tire manufacture. Is a sofler compound tire making the bikes behave strangely.