Here's how I fixed the mast thing that really irks me because there was no factory supplied method of controlling the mast while powering in heavy boat traffic or big ground swell.
I attached a line to the hole where the vang goes on the bottom of the mast. I ran that to a turning block on the starboard stanchion and then back by the winch to a jamclear i screwed into the deck. This works like a charm. I can easily reach the end of that line, and a good yank pulls the mast all the way to one side and keeps it there. No more will it slam as the yacht flounders over a three foot wall of death in a narrow canal.
One could simply remember to tie the mast base plate to the stanchion with a short piece of line or make a nice line up just the right size, with two snap hooks. However, to me it's such a vital control line that I was happy to spend a few bucks on a small block, two screws and a plastic jamcleat. I got the one with the fairlead built into it. The deck where I mounted it was quite thick enough to hold two one inch self tapping screws.
Here's some pictures of the mast control line
Ixneigh