Multi Rod, do you mean the DP ones specifically for MS or just soft bags in general?
I know DP ones fit on a set of brackets/frame similar to, if not same as, that for 'hard shell' panniers so no problem interfering with exhausts Ian.
I've got hard shell ones with which I also have the nylon internal lining bags. All-in-all pretty well made stuff and I'm sure soft panniers will be likewise.
Check out
www.multistrada.net web-site as loads of guys on there have even used other after-market kit.
Cheers!