The 109mm axle and the BB30 DS and NDS spacers are what you need. Might as well get the cannondale bearing shields and a new wavey washer whilst you are at it.
It's for the old Si / SiSL arms that have a slightly different profile. Using a 104mm axle with the new Si Hollowgram arms might give you chainline and chainstay clearance problems.
The 109mm axle and the BB30 DS and NDS spacers are what you need. Might as well get the cannondale bearing shields and a new wavey washer whilst you are at it.
http://www.cannondale.com/~/media/Files/PDF/Dorel/Cannondale/Common/Support/Accessories/SISL2_Road_Crankset_Instr_1012.ashx
I believe there's no difference in profile between the Si and SiSL2 arms.