I sail out of Chester (Gold River). If you were lake sailing, I wouldn't worry about it. But, as you are on the Atlantic, and losing a rudder could be a big deal, I would open it up, and have a look. I did that on my 1978 rudder last year. Turned out the internall SS frame was fine. As I had it open anyway, I welded extra stainess steel "fingers" and braces onto the existing framework. Then filled and reglassed the open side.
You only have to open up one side. If you can talk to any other Hughes
owners, who have done this, they may tell you that one side is easier to open up then the other. This was the case with mine, as it was built laying one side down, of course, and it seemed to have more solid glass encasing the rudder post and framework. Of course, I didn't twhat, and opened up the "beefier" side.
Before you cut one side out, tap everywhere and use a perma-marker to outline where it seems more hollow (and this easier to cut through).
I would not cut out the complete side, as I think it best to leave a few inches of old glass all the way around, so you can grind down the edge, at a 12:1 bevel or so, to allow room to reglass after. I also like that the ends of the tangs were still under the aft edge of the old skin, as I think that may make it stronger.
I have a workshop and welder about an hour outside of Halifax
. If your framework needs welding work, let me know. I may be able to help you out (if you don't have access to welding).
Here's a couple of pics of mine opened up. Usually, I don't believe that you would find all of the solid glass encasing the rudder post and tangs / fingers (which I had to cut away later, to see the existing gframework welds and then weld more to it).