yup,SB-28 is a very good flash,i got one too.But i find it too big to bring out as i only need a small fill for 5% of my Xpan use..
i use a piece of tissue strap with a rubber band when i shoot at 3m @F5.6 ASA400 to get some ambient in too.if i use it straight on will be at F8..
my own formula is ard 1piece of tissue per stop..

it works~!