The FZ6 uses a linkless rear suspension, so you’d have to replace the entire shock with a shorter unit...it’s not really an option.
I got a 'lowering link' and had it installed. It's been 46K miles, and no problems. I think it was this one:
Buy Soupy's FZ6 Lowering Link Kit (All Years): Lowering Kits - Amazon.com ✓ FREE DELIVERY possible on eligible purchaseswww.amazon.com
it brought down the seat height by about an inch and that was just enough for me (I'm 5'4")
I understand there are some reason why this is may not be a perfect solution (see Gary's post above), but I have not experienced any problems.