I've never had to use SFSSalv before. All I can think of is to make sure that the corrupted partition has plenty of disk buffers (1000+).
I'd be interested to know how it's become corrupted though. Does it even mount? What were you doing at the time of corruption?
Anyway, hope it speeds up a bit for you...
Maybe you could e-mail the author? He may be able to answer your question.