It is really interesting to learn how the different runner bottom designs evolved through the years. From what I've learned, my boat is a XH511 - Cole splashed this bottom and called it a TR1. After this design Irv made the runner a little deeper, removed a little bit of rocker, extended the chines to the transom and extended the air traps further forward - this became the XH511T design that was to be copied (and refined) by almost every other flatbottom manufacturer like the Cole TR2. Jim Lange has posted some great info on runnerbottom history / design on PB.
Bookmarks