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!