Hi Carsten, haha, true, we do like to sell them..and sail them, good one! 😀
Well, I would for sure take the Super Session 6.4 as the max size. The E Type fits better in the sizes 6.5 upwards to Freeride boards like the Blast and Gecko. Planing in 10-12knots is a pretty big call for a 85L board, but with right pumping technique, it's possible I suppose.
One board solution is great if you can make it work indeed, with some skills and a few fins/trim, for sure possible! good luck!