Hey Jon,
I can (and do) attach my boom brake to the s.s. rails welded to the deck --in the pic below, on either side of the main/amidships deck hatch, and right next to the oars on deck. Hard to see in the pic, but they allow me to attach the prevent well out of the way, so that the lines are not a tripping hazard...well, at least less of one, since as you know any line on a boat is a tripping hazard ;-) It's pretty easy to go forward, or work at the boom, without tripping on the boom brake lines.
We had one uncontrolled jibe, not catastrophic but not fun, this spring/summer up north that made me remember that I had a boom brake that came with the boat and that I had never got around to installing (as you know)...sure glad I have it. Still haven't finalized the installation, but I don't think I'll be leading the line to a dedicated winch, as I'd been thinking.
Cheers, Jud