You can of course eat more pb than that. I know a guy who competes ( he won the welterweight class at the North Americans this year), and he eats 12 tablespoons a day. After speaking with him, he says he takes no digestive aids etc... Granted, if I were going to eat that much, I would make sure I stayed regular. Seems like it would be hard to not stay constipated on that much pb, but he claims that isn't the case. Here are some links to his pics. Not a huge guy, but built well none the less...
http://contest.bodybuilding.com/bio/64182/