Discouragement on motor mount
Mark, I was thinking about the same idea a few seasons back. I too wanted more bite into the water with my regular length shaft outboard. However, I was discouraged from the idea for a couple of reasons.
First was practical: some posters suggested concerns about whether or not the existing mounting points would handle the additional weight of the bracket & outboard, plus the additional torque/leverage of the outboard being held further away from the mounting point.
The second was purely aesthetic: our 23.5s have such a pretty, elegant sugar-scoop transom. A bracket would clutter it up and detract from the beauty.
In the end, I just upgraded the whole shabang, ditching my 17-year-old, 6 hp 2-stroke for new 9.9, 4-stroke long shaft. Couldn't be happier.