[Espeefan]

For what it's worth, a fully charged 3S LiPo has a nominal voltage of 12.6, and a 10 cell NiMh pack can have a nominal voltage of up to 14.5, when it's fully charged, but the voltage will drop off faster on the NiMh pack, to it's normal 1.2 to 1.1 volt per cell range. At that point, I would say the FX-R would handle a 10 cell NiMh pack, but I'm not sure if I would try running a freshly charged one. It could be to much. If you let the NiMh pack sit a while, and waited for the cells to drop a little, I wouldn't be worried about over volting the FX-R. Maybe check the voltage with a multi-meter and watch it.

Or just get yourself some 3S LiPo packs. I used to be scared of running LiPos too, but I finally took the plunge. Treat them right, always follow the safety tips, and they will be just fine. Is there a reason you don't want to run LiPos?