Frankly, I beg to differ. After trying with and without straps, I understand now why SUP foiling did not take off 7 years ago when Bruno Andre pioneered it and made a production foil and board offering:
- it is insanely hard without straps
- being positioned in the rear makes the board un-balanced in the air, with a huge swing weight far away up front, and wind catching issues that even made Bruno dig a hole in the front of his board to let the air pass through...
- it is slow as hell to paddle
And I could find many videos of people SUPing strapped (Kalama, Laird, ...) (*).
I would just ask you to ponder this fact: If I was to cut the last 33cm/13" of my board at the tail, I will have exactly the measurements that you recommend, both for the foil and foot placement. It is like I am using a 7'8" board now, with 13" added for paddling efficiency but out of the way in flight.
And in the opposite: consider adding 1' of tail to your board: it will not change anything in the air, it will just make it faster to paddle.
Note that I actually considered cutting 1' at the tail of my board once having progressed, to ease pumping (the tail can drag a bit in the water on pumping close to it) and gain some weight. But frankly, is it worth it considering that you ruin the paddling speed to be able to fetch foiling spots far away from the crowds?
In my opinion, with a foil in the rear, you are forced to move a lot forward on the board to be able to take off, that's why you think you need to have the feet free to move back in the flying position. But the trick of the centered position is to make the paddling position efficient for take off the same as the one for flying!
Basically you may feel you need to have to move your feet... because your feet are not on the proper position to begin with.
(*) Here is one with Austin Kalama. Note how when he paddles his feet are around the front footstrap. Since I paddle with the feet between the 2 straps, his paddling position would be the one I would have if I was to cut the last 1' of my board.