If you go the shunt bypass route, I'd do it with some alligator clips and jumper wire to see if that really solves it before I'd start soldering. My 2 cents.
It sounds like the vendor is instructing you to bypass one of the two banks of shunts. I've never pulled one of those things apart or seen a circuit diagram so it's hard to say. May be a good idea to sketch something out showing what you are planning to do, scan and email it to him for clarification.