We copied Kimberlite's solution that Eric showed us in NY and have been most happy with it:
Take the Amel factory preventers, and duplicate. Make the lines a bit longer so the unused preventer can run when the boom is on the other side. Leave installed any time you go sailing. Leave preventers loose (unstopped) if braking is unneeded, such as when going upwind. You forget they're there.
We put one soft shackle on each of the booms, and we attach the preventers to the soft shackle. Less noise, less scratching, and exactly what Amel does on the 55. I think it is the same Amel did on the 54?
We did, plus we added one block to the mainsail preventers, so the brake is right next to the cockpit (next to the boat's lift point) so it is much, much easier to unlock the brake than with the Amel original. We love the system.
Funny thing is, we've been carrying a brand new Wichard boom brake in its original box since a little before we met Eric. Someday when we get back Stateside we'll put it on eBay!
SM2K n. 350
At anchor, Mar Menor (near Cartagena)