To start I want to say that I used 3 layers of the same supersaw and panning for larger image stereo. First take a sample of the supersaw and shipping to a channel of the mixer all left and then another sent exclusively to the right and leave the principal in the Center already with this is this expanding more spectrum estreo, only is playing with frequencies in the EQ so that it is as you want it to sound the supersaw.

Also usually use tools like which brings the fl studio both the stereo shaper and the fruity stereo enhancer or the famous stereo image S1 waves plugins is very good to extend the area stereo otherwise serious export in wav every sound in this case supersaw and pass them through the imaging tool stereo iZotope ozone 5 6 or 7