I just started the second season with my Zelos and think it?s great.
When I purchased the boat I also purchased the Horizon recommended Reaction 2.0 5000mAh 50c x 4 and IMHO are good batteries.
Shortly after I ordered 4x SMC 7400mAh 75c and experienced a pretty big difference, although they swell. One of them even split the hard case.
I?m thinking of getting some more batteries and would like to know of any success or issues you might have had.