You don't mention alternate file systems, but If you switch to PFS or SFS file system I believe they'd let you use the entire capacity of the drive and AFAIK they work under 3.1/3.0. You might have problems with some older software if it tries to write to partition space beyond what the Amiga could normally address, however.
Probably best to wait for a more complete answer from Thomas.
Edit: nevermind, I see you did mention SFS. D'oh!
