The voltage limit at most races in the US is 8.40v, and the ROAR races have a limit of 1C charge rate.

For discharging, don't go below 3.0v per cell, so 6.0v for a 2s pack, or you'll kill the pack. To be safe, I'd limit it to 3.2v per cell, or 6.4v.

That said, you really don't need to cycle the packs. Just leave the remaining charge in them after your race until the next race day. Then just charge and go.