We hosted a race this weekend, and I believe we followed the spirit of the rules. If your car weighed 1417, you were allowed to run and told to correct it before the next round. Batteries at 8.41 were given the same consideration. These people weren't trying to cheat, and we didn't have any repeat offenders. If a car was presented at 1380g or 8.5, you were DQ'ed (no one did this). It was explained at the drivers meeting that the rules were in place for safety and equal racing. I think that we achieved that. After the first couple of rounds, we had racers tech'ing each others cars. I tech your car, you tech my car. I'm not going to let you cheat and you're not going to let me. It worked out well and we had a great time.
Back to chargers. If voltage over 8.4 is dangerous, why do some have a "competition" mode that peaks at 8.5? Funny that this same charger shows the same 8.4 volts on the screen but shows 8.5 on the VM.