It's my understanding that 8 1/2" was a semi standard for WJ. The position from rail, toe, and cant are quite different from "modern" multi-fin surfboards. Before I scrubbed these last two boards , about 7" was where I was getting to and scaling fins down as I moved back. The fins I'm current running are 5 3/8"h x 5"b with what I would consider a fair amount of rake and a full tip ( with a non GG approved zit on the tip )