Parallel charging might be OK if you have all good batteries. Even if the cells have different internal resistance during charging, the weak ones should catch up during the constant-voltage charging phase. I would worry, though, that a battery could have an undetected bad cell that would show up in an overhead eight. Also, hooking up these powerful, low-IR batteries in parallel seems like a bad idea to me. I checked battery voltage before hooking two in parallel and still one pair of cells was sufficiently different to smoke a trace on my board. Then there is the issue of having a live, exposed male connector while you're connecting them. Parallel-hookup boards for LiPo batteries should have some monitoring circuitry.