Dave, I just mounted the seat in my CF Nokomis.
From the top of my seat front, to the top of my inwhale, is about, 4". The back is about 5/8" less. This makes the seat much more comfortable !
I Drilled my hanger bolt holes, as straight up and down as I could. This way , if I want to change the seat height, everything should line up.
If you angle drill, you are bound to stay at that height , unless you redrill .
My hull is tumblehomed similar to yours. I 'll go to the shop, and get some pics of Nokomis's seat today.
Jim