I was over at my LHS and saw that Orion has a 2S stick pack LiFe the same size as the standard LiPo. Reading the ROAR rules, I see that LiFe is also accepted as an option in many classes to LiPo.
LiFe is a fantastic cell. Tough as nails, loooong life. high discharge capabilities, etc., but it is only 6.6V. As a great as it is, who is actually racing with a 2S LiFe?