Neither do I! I was planning on using rear disc brakes on my new build, but it turns out that I don't have room. Then I discovered this: V-Brake Plate by MISC It's an adapter that allows you to put V-brakes on any bike frame. I can't find a really good picture of it installed, but as I understand it, you bolt it on through that hole at the top to the fender mount, and then use hose clamps through the slots to fork. I ordered one, will post pics once it's installed if anyone is interested.