"However you'll be surprised how little grip you will have in the arena on those big wheels."
Alan those wheels aren't big
I do agree with Alan on over volting motors. if the optimum volts are 24 then that is the target to aim for reliability wins fights. I would start off with simple and reliable then modify from there. for an example Gabriel in the World Champs uses 24V motors running on 22.2V. I don't think anyone would say it is slow or underpowered.
I would argue over volting is done as a result of desperation, rather than design.
looking forward to seeing your robot in the arena soon.
Craig