Odd alright, don,t use a gybe preventer myself but sailed on a 32ft sloop a couple of years ago in rough weather round the Isle of White, UK.
As far as I could tell the Gybe preventer was much the same as the headsail sheets, 5/8" or there abouts. Attached to the end of the boom and could be rigged fairly handily by some clever mechanism I didn,t take much note off.
There was a recent thread about Gybing with was a lot of discussion about a gybe brake, seemed a safer bet to me.
The great appear great because you are on your knees. James Larkin, Irish Labour Movement.