Yours sounds like it's about all the way out, so the rear is about as high as it will go. When it's on the centerstand is the rear wheel on or almost on the ground?
From my understanding, and I just bought an adjuster on Ebay so I'll be an expert soon....they sound easy to experiment with.
Loosen the two nuts (ones left threads) and shorten the adjuster and the rear wheel should move higher off the ground which should make the sidestand work better.
But remember, you'll be increasing the rake/trail so the bike won't seem as quick turning.
But remember, right now I'm just guessing, so this info is worth what you paid for it....
2004 ST4s ABS