If you max out the rate of flow IN and still are running the bowl dry, then a bigger bowl would be necessary. More than likely the bigger bowl is a precaution that these guys are taking. I mean if they aren't flowing enough fuel to begin with, and are sucking "normal" size bowls dry, these guys are going 300 ft to an 1/8th mile at a time. It's not like it's a trail motor or dune motor or something to just go cruise around on. They run their run, either shut the bike off or idle back. If they run the bowl out at the end of the run it doesn't really matter.