Neu energy battery ?s Help!

i have a neu battery , 4s 5k pack , and i just finished breaking it in (not discharged less then 14.8v for 5 cycles) , but i have decided that i should have gotten a 5s pack

i just cant seem to get the speed i want for bashing

what can i do, the pack has been run so i cant return it and i contacted neu and they do not sell cells as there packs come pre-built

do i just keep the 4s for running on the track , which isnt very often right now

should i sell it and take the loss to get a 5s pack ?

should i buy a 3s 5k pack and make my 4s a 5s and then sell the 2s pack ?

does anyone have a neu pack that has a bad cell that i could buy(not a good idea) to make this a 5s pack ?

suggestions?

thanks