i have a 5800 and i run smc 4200 6 cell on them, im getting about 36-37 mph on them, i also have ib 3600 7 cell and im getting about 38mph on those, really not much improvement over the 6 cell smc IMO. then i also have 1 set of 7 cell elite 4300 and with that i got 39-40 mph, this is all tested with the bushnell velocity speed gun. i was getting better numbers when i was using gps but i think the speed gun is more right on. i plan in the summer summer to buy lipo and do more speed runs then. [>:]