Although in general I'm a big fan of reflective material, ISTM that for side lighting it's not optimal. Reflectors only work when there's a light source near the observer's eye (like a headlight) that is hitting the reflector, and for side lighting, you're not in the headlight beam until it's too late to be useful.
I think side lighting needs to be active as well.
Personally I think I'd mount two PBSF's on my seat post, pointing nearly straight out to either side (a little to the back). Right now I'm running a Dinotte straight back and a PBSF on my helmet.
I'm not going to do anything myself though, because my route is almost entirely rural and there simply isn't any side impact threat on my route. I do not pass any significant side street or other road entrance where it's a factor. I run the Dinotte because what IS a factor on my ride is cars coming up from behind at 60 MPH.
__________________
Work: the 8 hours that separates bike rides.