i live near the guy that did the machineing and assembling and we are friends so i help him with his electrician needs.

he gets a lot of "balanced" rotating assemblys and sometimes his mesured weights and the written down ones are way off and the crank jumps around like mad with the their bob weight to just check quick.

it is my experience if you have a trusted shop then let them do the balance. a good shop will check the balance if they are going to be that guy anyway so why pay twice to do it correctly?