how many rounds do you have like!?
my club has on average 5 and i start charging my packs before practise on a 3 step charge, at 3 amp then 4 amp then 5 amp then im ready to go.
if you think your getting an edge by doing them between rounds belive me youl loose that edge in the practise lap you do :P the performance wont drop within the amount of time you have till your next race at meetings. i dont go over 5.5 amp just to keep my cells in good condition in the long run, ive tried charging at silly amp before and i just cant justify it, if you want to go faster put in a faster motor