gsxr rear shock body weight suspension adjustment

Do set the preload first, front and rear. That may not help. If it doesn't, then you have some ride height adjustment to do.

Depending on the year GSXR shock it could be shorter than the original shock. What you're describing sounds like you've lowered the rear end relative to the front (shorter shock). This increases straight line stability but makes turn-in more sluggish. You can raise the fork tubes in the triple clamps to lower the front relative to the rear. Try 5mm at first and then steps of 3mm until it feels right for you. Don't lower the front too much or you may wind up with fender/radiator banging together on bumps or heavy braking. The limit is around 15mm, if I recall correctly. Check this out.

The referenced article is a good method for setting preload. However, I always take issue with the statement that less sag/more preload is a stiffer setting. Preload sets only ride height (and so the position of the suspension in its stroke). It doesn't change anything else.

Example: Suppose you've got a 50#/inch spring, preload 2", total load on that fork leg 150#. (2" preload X 50#/inch + 1" sag X 50#/inch) = 150#, so you'll have 1" of sag. To compress the forks an additional inch takes an additional 50#.

Let's crank the preload up to 2 1/2". (2 1/2" preload X 50#/inch + 1/2" sag X50#/inch) = 150#, so you'll have 1/2" sag, the bike will ride 1/2" higher. It still takes an additional 50# to compress the forks an additional inch.

So nothing changes but the ride height, which is important enough. There is no valid reason to change the preload between street and track.