Found and played with those spring tension adjustment screws and managed to make the back brakes pretty functional.Also improved the angles so the cable moves smoother.The front ones are now quite excellent.the back brakes are too squishy so I am going to check and lube the housings next.I never had new brakes before.The brakes are very powerful and also noisy.Will that improve as I wear them in?Appreciate your advice on liability.All people will sign a personal injury waiver at the very least but I fear insurance will be prohibitively expensive and make it impossible to turn a profit.We'll see.As far as a LBS putting these bikes together I consider myself competent to do it myself as well as Maintain them.I never had experience with these types of brakes before however.Thanks for your input!!