What’s a good clark blank for a knee board?
The description for the 6’2"C is “Designed to make kneeboards or modern fishes up to 6’2”, so that might be a good bet.
Just made a 6’ kneeboard from a 6 2 c, it was designed for such. If you are in Oz, Burford make kneeboard blanks as do Dion. If you are going fish style maybe want a flatter rocker such as a Clark 6 7 A.