The surface mount Ion is different than the universal mount Ion. The housing of the surface mount Ion is the flange. The flange is not a separate part that you can add to a universal mount Ion.
Do you have the surface mount Ions or the Universal ones?
If you had two of each, you could put a couple of new holes in the push bar for mounting the side ones using surface mount. Your forward facing ones would have to use the universal bracket type.
Also, Whelen does list a bail bracket type, the ION1KB (for universals).
[Broken External Image]:http://www.whelen.com/images/_automotive/Dash_and_Deck/ION/ionkb-lft.jpg