I was always a bit uncertain about the snap - but mine just sits brushing the deck when close hauled and leaves the boom with about the right amount of offset so I never bothered to question it. I didn't build mine, I just bought it second hand and got the manual to sort out bits that didn't seem right that the previous owner had left to get it working to my satisfaction.
It was quite possible that with the rigging looking like badly hung washing, that the resulting lack of performance was the reason it was being sold. On the other hand, all the bits of string might have been just thrown on to show that they were there to ensure a sale. Looking at the strange and unlikely places that epoxy had been applied, or allowed to run to, I suspect the former. Reading the instructions and following them transformed it from a plastic log into a good performer.
Q Is your pivot line tied to the deck eye? Mine goes from the boom fitting, through the deck Eye and back to the starboard cleat by the mast, where it is made off. I took the 12mm to be the length of string from fitting to deck eye. Should I feel the need to change things, I will use tiger's tip of clamping the line under the cleat.