I bought a divider from Petsmart like the one you mentioned. Its totally crap! It does sound like a good idea, and maybe a different brand would work better. The one I bought came rolled up in a tiny tube. Its almost impossible to get the kinky twist out of, and once in the tank it curves around and doesn't hold right. I tried to use suction cups to keep the divider in place...no joy. I used it for bettas and both betta would wonder to which ever side they pleased. (now my female is almost torn in two pieces (well not literaly) because the male beat the ever living daylights out of her.)
So I wouldn't recommend buying the dividers that come wrapped or rolled up, its darn near impossible to keep it straight in the tank. My bettas seemed to sleep right under the bottom, or along the bottom sides because the sealers on the side of the plastic netting would not stay flesh up against the sides.
Needless to say...I'm returning mine, and buying one that comes flat, if there is such a thing. I even tried laying books on mine to flatted it out, I pick it back up and it just springs back into a coil.