What causes tomatoes to split? I never can remember the accepted theory on that one. A lot of mine are splitting pretty badly so far this summer.
By the way, I just picked my very first Marianna's Peace tomato today. It was one of the few large ones that did not split. It was approx. a pound or slightly larger, and tasted to me very much like a pink brandywine. The vines are beautiful and have lots of large pink tomatoes on them.