Mitchell Rae from Outer Island Surfboards is not to be forgotton.
He has been doing flex tails for as long as I can remember in short boards and more recently longboards.
The first one I remember seeing was early eighties on the Sunshine Coast.
I've got a 6'7" rounded pin carbon flex tail short board.
Great fun in powerful waves where you can really get the tail flexing.
Mitchell resolved the reduced volume issue......see photo.
Would work for a SUP.
How's the way the centre fin is glasse on....to allow more flex in the tail.
The guy is a shaping guru!!