If you get the ProJump cuffs, you can try with the plastic projump brackets, but I know Ricky from Swansea in Wales had riSers and put the projump brackets on and they didn't hold, so he had to get 7League metal brackets.
I would say buy the 7's cuffs as then you get the metal brackets with them, saves a lot of faffing around and the cuffs with definately be secure.
That's only for people who have 7's or PoweriSers though, if you've got ProJumps you're better off getting the ProJump cuffs