You are right, I think. I am against formula. Well, actually, I really enjoyed my formula boards when I had one But the really large sails don't work well where I live. The wind here can triple in velocity in the blink of an eye. When I used the formula board and sails larger than 8.5, I often had bad experiences---out on the water, having a great day of planing, and then all of sudden the whole lake was boiling. It is not like living on the coast where the wind can blow 14 all day long. Here it blows 14 and dies or blows 14 and then goes up to 40.
So my problem with formula boards is that I don't think I need one for an 8.5. In fact, 8.5 seems a little small to get much benefit from a formula board.
Thanks for the advice. I will research the Isonics. My one fear is that the footstraps may be hard to get into.