I kept myself occupied trying to work out a formula in my head for VMG as a function of tack angle. 120 makes it easy and I believe leads to VMG = V/2. If I was able to tack through 90 degrees AWA as performance boats surely can, that would improve to V/sq(2). I'm sure there's a general formula involving a trig function, but I couldn't quite figure it out without pencil and paper