I don't think you want a front brake on a fork with round blades *and* a front tyre that close to the downtube. If the front tyre ever touches the downtube, it will pitch you over the bars before you can say "ah bugger" and quite possibly bend the fork beyond repair. The rapid deceleration caused by braking *and* tyre-tube contact bends the fork more, it grabs harder, this bends the fork more, it grabs even harder...