No one i know has this problem.
I think the speedo is designed to handle a voltage a tiny bit over their rated volt rates.

Dont try this at home, but Rexs Challenge (RRC) 24v speed controllers can handle 32v

Im sure they took into account that fully charged batteries will give out a higher voltage at the start. Many roboteers use those speed controllers using 24vs worth of Nicads and SLAs, and all seems fine.

Mr Stu