You could use some velcro straps and try different sizes.
If they dont work just get rid of the velcro.
A buddy of mine uses them on a big bird (9 foot span)that he uses to get sailplanes up in the air. He sais it makes a big difference, stall speed is much lower. They are about 3 times as fat a the wing, the shape doesnt matter, square or round make your choice.
I have never seen a study, im interested in aerodynamics but dont know much about it (yet, gonna go for civilian pilot study next year)

Hope this helps