My 03 H17 was very loose a few years ago, so I had a local glass expert route out a pocket and install a block of a hard glass substance I believe was called G10 in order to firm up the connection between the cross-bar end casting and the hull. It was an okay solution. The epoxying of the cross-bar beds would have made it better, but if you study the geometry of the situation, you will see that even that is not going to last in areas where there is heavy chop.
I wanted a permanent solution, so I got a guy (?Lentz? of NC, from this forum) to cut-out and send me hull sections from a 17 cadaver so I could study the problem and come up with a fix that was both DIY and tightenable over time. I came up with a fix (the general idea is represented below) , but never tried it on my boat.
Here are some pics with some quick and dirty annotations and a funky representation of the fix I mentioned.
Other ideas include adding structural brackets to the top-side. Or, a cable/bolt affair which would attach the same way the shroud chain-plate anchors do (under the lip), come up through a hole through the hull lip, and anchor via a cable over the end-cap "hump" onto the top of the cross bar. All of these are major projects with too much sailing down time for me to even think about.
Enjoy the pics!