Not sure I've ever seen a 5000mah sub-C cell, or if there was one labeled as such I'd be leery. The last sub-C's that were raced were the IB-WC's and they were finicky as hell...and "only" 3800mah. I say "only" because I remember racing 8-minute 1/12 "mod" (it was all "mod" then) with Sanyo SC1200's.