John --
My thought was to put the base as close as possible to the vertical side of he motor well which is the starboard lazarette and a bit aft in the motor well. I have been thinking about epoxying a piece of 3/4" plywood to the motor well on the upper side and filling the gap between the plywood and the vertical side with thickened epoxy. Then, epoxying the wedge to the plywood base and setting the davit base on the wedge by drilling oversized holes in it, filling them with thickened epoxy and dropping machine screws into the epoxy before it sets. I have installed cleats in this manner (machine screws into thickened epoxy in oversized holes) on another boat and it worked well. My thought is that I have never feared to stand on the motor well and I am 200 pounds. Therefore, if the davit has something on top of the motor well to spread the load a bit, it should be able to take the less than 100 pounds I will be lifting with it. The one concern I had was that the upper ring bracket support for the davit is not very high at about half the distance above the base that it would be with a mount on the floor boards.
What had me thinking about the motor well mount was the length, even of the longer arm, and the inability to have the end of the arm over the motor to set it on the bracket. The counter is that with the davit taking most of the load, it should be relatively easy to pull the motor out (aft) so it will land properly on the motor bracket.
So, like you, still puzzling! Thanks again.
Jim