Why does anyone bother to read Chocotaco? He's not Primal.
Knifegill's problems digesting starch is clearly an outlier.
To the Original Poster.... Mark has an extremely thin build. His calf muscles are too thin compared to the rest of his body. He probably has more trouble keeping the muscle on than keeping the fat off. Please just look like yourself. But for breaking through a plateau, the fitness forum has a lot of advice.
5'0" female, 44 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently keeping food tracker.
I (try to) follow by-the-book primal as advocated by Mark Sisson, except for whey powder and a bit of cream. I advocate a two-month strict adjustment for newbies. But everybody is different and should tweak Primal to their own needs.