Had the same issue and did a couple things:

1) Custom fabed a steel spacer from a .020 thick washer I bought off MCMaster Carr to space the inner clutch hub out to give the basket more room to spin freely.  Washer needs to be the same ID & OD as the bearing and goes in between the bearing (part #3) and the washer (Part #5) on the clutch fische.  This will widen the clearance the outer basket has to spin inside of and let it spin free-er.   This can be done up to .030 but that is pushing it.
http://www.suzukipartshouse.com/oemparts/a/suz/50d09297f870022e9cc419d7/clutch

2) I also used a professional grinding stone (absolutely 100% level) and VERY CAREFULLY lapped about  .005 off the back of the drive gear on the clutch basket.  Which lets the basket also spin free-re.

3) I sent my tranny off to WCR for their undercut, cryoed, and micro polish.  I've heard price ranges from $175 for for the first guys to do it up to $250 when Greg's trying to set expectations.  I paid $200 but had to follow up many times with him as he blamed it on the wife for not shipping out BUT I did get it back, the cutting was done well, BUT double check your washer stack as it came back with one washer on the wrong side.


I F-D with mine for almost a full season before I got it fixed and what really fixed it was sending it to WCR and running Type-F in the tranny which you need to change every 10 hours or so.