PLBman.....Like others have stated I would just match up the runtime as close as you can per 6 cells. The change in voltage is not as big as running a 360 cell with a 410 cell would be. Just try to keep the Runtime close in the whole pack as best you can. If you have any more questions feel free to ask them in the Hurricane thread or give Brad a call at the shop....or if you race On-raod look for me or Brad at RSJ raceways we will help you out.