Billyruffn, your system is very rare. I can't recall ever seeing one like that. How would one experience an "accidental jibe" with this system connected?
I was using an incorrect term. I was referring to the mainsail going aback -- you're right, technically you don't jibe unless the boom comes across. I've never had a jibe with the preventer rigged, but frequently had the sails unexpectedly go aback. When the wind's up and the swells are big that's no fun either.