I'm still antiquated in this area on Xmas. The boom end fitting has loops for snatch blocks. A 2 part was attached at the boom end, the other block shackled to a bronze eye that threads into a deck insert, about midway along the deck. Because the boom is roller furled, a strap we use (as a vang) isn't too handy. I rigged this as much to shape the main as prevent a gybe.

The preventer didn't have the angle to stop the boom rise but I think it contributed to minimize the gybe, that and the backstay.

I'm still resolving how to rig a new main(this one if finally showing the end is near, but I'm surprised we didn't kill it that night, our new genoa has to go back to the sailmaker for some resewing after that blow) with the spruce boom. Slab reefing for sure but not sure about the best vang system.