Personally I think a front is sufficient on a fixed gear, but you're right about positioning it near the stem a la cross, it is still good for lazy riding and cruising but for an emergency stop it becomes something next to useless unless you're 0% body fat and primed with an arm of solid steel. You need both hands on the bars and balanced to properly execute an emergency stop at speed. I mean a real emergency stop, whatever to zero in a car length or less. If it's just there for a downhill you're got too many inches for and such it's fine, but stopping instantly...changing hand positions is bad enough but making up for the fact your braking arm is going to be under a lot of stress handling a greater amount of your foward momentum and causing it all that force to rotate....smack the face on the ground, always on the brake side too I'd bet.