This is helpful, but I have a followup focused on the compression tube:

How important is the compression tube? Any helpful hints on placing it inside the crossbar during installation?

I just bought up a used Nacra 5.0 with a damaged mast support rod. The previous owner had forced an incompatible mast ball onto the old (too large? custom?)rod causing the ball to explode while we were trying to step the mast. The threads on the top 3/4" of the old rod were ground off compared to about 1/2" on the new smaller-diameter replacement Murray Marine mailed to me. I've removed the old rod (it was so corroded/battered I had to hacksaw through it), and am preparing to install the replacement, but realized the previous owner installed the old compression tube around the support rod between the dolphin striker and the crossbar (!?) instead of inside the crossbar. The old compression tube is sun damaged and can't be removed from old rod. I didn't order a new compression tube (didn't know I should have till now). How big of a deal would it be to continue to sail this boat without a compression tube (obviously it has been done for a while now).