You are perfectly ok to fit any cuffs to any bocks I have done all of them except Powerisers and have seen them fitted
It is also possible to swap any spring onto any frame (with a little bit of alteration) and most parts from most bocks will fit others with again a little bit of work
Only problems with the cuffs are that 7 brackets and some earlier models of other Bocks are made of a softer plastic and won't hold them tight enough
Skip brackets are totally different and can be tightened up enought to tow a car
I have in my collection several sets of "Bitsers)
1 Skip uprights and walking feet /Projump feet, springs and support bracket /Homemade cuffs, bindings and hoofies (all on one set)
2 Projump uprights, springs, support bracket and feet /Homemade walking feet, bindings and cuffs
3 Projump frames with Skip springs fitted (2 pairs)
I have in the past fitted 7 springs to Projump and Powerizer frames with total success
And if you have any doubts about Skip/Projump frames ask Tim as he came bl**dy close to flying on mine
Jason
Ps all my feet/hoofs are PJ bolton ones as they are the only type I have found that you can change the rubbers and they don't break
PPs before anyone says Skip hoofs they are good but I can't afford them