"lthough Sheldon Brown has advocated mounting brakes to only the front hole of forks, which provides even less vertical support, I don't think he tried it with small wheels."

The 2006 Dahon Hammerhead had the front brake mounted on the rear of the front fork. It looked nuts. (20" wheels) A fix for too short a reach is a drop bracket. Sheldon made some.

I made mine out of 1/8" flat alloy bar and put short reach Ultegra brakes on the Hammerhead. They didn't stop any better than the back-to-front OEM caliper. Sold the bike. No brakes = nuts.