Engineering principles aside, HOW would I install a new compression tube inside the main beam?
Does it simply slide in from the top along with the mast rod, or does it need to be inserted from the side through the end of the main beam?
From the side.
Drop a small nut attached to a small but long line through the top hole so it goes out at the bottom. Tie the end together so the line cannot get out.
Then slide a long pole (your tiller extension for example) to push the line in the beam sideways all the way to one side. So you end up with one continuous line with one loop around the beam and one loop exiting the beam on one side.
Rotate the line until the knot is on the loop on the side of the beam, untie the knot, slide the compression tube on the line, tie the knot to make it whole again. Then you just have to pull on the loop around the beam until the compression tube is in place.
