The Pin... I think this is some homemade DYS project. I would not expect that the way the pin is installed that it will do much about the flex issue.
Once you remove the corner castings it is very interesting to see how much aluminum has been rubbed off on the pylons. It is reasonable to assume that the a similar amount has rubbed off on the castings as well. In side the casting it is kind of more difficult to tell.
I do not like the idea of permanently epoxying the corner castings to the pylon - it is a good idea in terms of getting the flex out - but it is very permanent.
I shimmed my boat with brass sheet metal. I did not use the kit that Hobie sells. I used full sleeves. Got that stuff for $5 at a local sheet metal place. It worked well – very little flex now. I also replaced a good number of rivets - corner casting to x bar. Especially the one in the rear gets flexible. The X bar in the front seems to have a lot less flex - might be the dolphin striker design.
Bolting the castings to the pylons… The before describe way seems like a possible solution – since some type of spreader was installed inside the pylon. IIRC the corner castings cannot handle much pressure / torque. A good indicator for that is that the hobies originally had nylon nuts holding the corner casting and the pylon together.

Patrick Koch