I've re-configured maxamps packs. I had a 3s 8400mah pack that came as a square brick. I reconfigured it into a long brick. I changed a second pack into a 4s 6300mah pack which I later changed to a 4s 4200mah pack.
my cells were soldered together which made it easier, but this isn't something for the faint of heart. Taking apart and re-assembling lipos is a potentially dangerous thing and extreame care must be taken to ensure the cells are connected properly and that they don't get shorted out.
Current active RC's; Brushless Xray XB8, CRC Pro10, Tamiya M03, Xray M18, Losi Micro-T. Inactive list; Losi XXX-S, Duratrax Evader st, Traxxas TRX-1, Traxxas E-maxx, Brushless Ofna 9.5, Corally sp12m