It generally went OK but I had limited success with tapping the plate to accept the bolts. The metal is quite poor quality, no wonder it snapped, and was too thin to take a tap successfully. For now I have riveted it on but this is not a good permanent solution. I will have to drill above the two rivets and secure through with a nut and bolt. The bolt head will be able to sit nicely in the sail slug track.
I am, once again, running out of time and have got sooo much to do!