I think that you need to play way more hands before you can feel confident that you will win more playing at 15/30 or 30/60. That being said, i too win more playing 10/20 or 15/30 as compared to smaller limits and i'm not positive why either. I thought the same as u for awhile, because there aren't as many stupid fish; however, Sklansky will quickly point out that these stupid calls should make you money in the long run, but for me it doesn't seem like they do!