In simple form here is a picture of the bottom of the board.
Note: I now mark the CG on the bottom of all my boards and using a silver paint pen to note the distance from CG to the side of the base plate. A thin strip of clear packaging tape helps preserve the ink.
5.3" back from CG to Leading Edge of Mast / First Set of Bolts.
Be done with this Puh-hoooyeee of measuring the distance from the tail. There is no objective way to do that with boards ranging from 7’ to 10’. I have a pro-level rider in the neighborhood and we have standardized on this metric. He is running 5.5" behind CG with his Advanced+ fuselages.
