Comment to your report in Maritime Feedback No 20 entitled “Human Boom Preventer”.
The major problem with just supplying a length of rope as a boom preventer is its awkwardness to fit, especially in the heat of a race. These preventers are rarely if ever pre-rigged, indeed it is awkward to do so!
This inconvenience is the major reason why the preventers are never used. A more convenient system is to have the preventer in two parts.
One part is a rope secured permanently to the outboard end of the boom, with the other end of the rope clipped temporarily at the inboard end, e.g. to the kicker fitting. The other part of the preventer is a rope led forward to a block on the gunwale, then back to the cockpit.
To rig it is then easy to unclip the first part from the boom and re-clip to the gunwale-rigged line and tighten as required.