When the shop balanced the crankshaft, did they have the balancer and flex plate you are currently running? If not, were you charged for heavy metal or mallory metal as part of the balance job?
I am actually wondering if they internally balanced your rotating assembly to neutral balance? This would make the flex plate and balancer wrong for this application.
Ask the shop that balanced it specifically how they set it up, internally or externally, before you go changing up your combo.