I'm an electric RC airplane nut so I'm already familiar with all the impellers and motor/esc combos you guys are using. I don't see any reason at all not to change your "C" battery tubes to be strings of lithium polymer batteries in series and parallel to give you much greater run time. The weight offset could be corrected using a little lead to make up for the lighter LiPo battery packs. Being rechargeable is a huge plus as well, but the longer run time would be huge in my intended use.
Have we discussed this before and i missed it, it can't really be considered cost-prohibitive since we are building ROV's. LOL The previous charging problems with LiPo's have been rectified by using balancing chargers that use a simple wiring harness to charge each cell individually. I am new to ROV's, but I can't really see an issue using them unless the PCBs are not compatible with the voltage combos of the 3.6v cells. Why aren't we already using LiPos for more run time and rechargeability?