Look at Ronnie early in his career. He was pretty tubby compared to today. Mark Allen, Shane Thompson, Shaun Murphy, Buddy Hall, and, of course Bill Werbeniuk, have all won while well overweight. Regardless, Cousins can move around well, and weight doesn't seem to be an issue.
Both Bergman and Cousins played great. Bergman is generally a slow starter, and while Cousins didn't play great for the first 5-10 frames, he played well enough to win. After that, Justin seemed to have his number. A longer race to 50 or so would be interesting, and I think would work well for Bergman.