alexmf2,
I think that, at least at first, 2 Eviolite is the way to go because you are garunteed to attack twice, even if you flip double tails and the opponent hits for 150. Until we see what the main metagame consists of, we really can't reliably run Rocky Helmet. It's not as consistently useful as Eviolite. Plus, you can really abuse SSU in ReshiBoar, so making sure that Reshiram EX doesn't go down is more important than getting faster KO's off. I think ReshiBoar has a much better long-haul game than the other EX's do because of that. Now, if the format gets flooded with 100 HP Pokemon and 170 HP Pokemon, we can go back and reconsider, but for now, I gotta go with 2 Eviolites.