remember mine was a home made set for a 1/6 scale Goldberg Cub( a little smaller), believe it or not I used a combination of small Sig rubber bands and "Goodies" hair bands from Wally World... dont laugh! it worked great! I would go to Harbor Freight and buy the O-Ring assortment (8 bucks or so) and experiment. It takes more force than you think to make the bungees work right. Dont use too many though as it will have no spring, put it on the ground and roll it out to get a feel for the right amount. I see that on pictures of the Robart gear they use 4 O-rings it looks like, 2 on each keeper. I used very small O-rings to keep the bungee covers where I wanted them, invisible if you use black material.