Ignore vfm and get something that fits. A brake that does not fit, may not work (or damage the bike). The goal of the brake is to work when you NEED it. Point 2, are you sure the bike is OK to set up as a fixie? Apart from a different set of stresses, the chain lines are also different between multi-speed and single speed. You are imposing a non-standard condition on a very specific frame design. Point 3, a "real" fixie has nuts to hold the axle on the frame. You want that wheel rigidly held. If you get the axle tight enough with a quick release, you may damage the dropouts. A damaged dropout may break, which is not a desirable outcome.
