Adding pounds to you rotating mass isn't going to help the goal of faster...unless either your power is so high or the stability of your crank so low you have to have it. Agreed that sharing the weight mass of 2 through the center of the crank is stressful without them. Why carry them down the track, or have to accelerate them on every shift if you aren't overloading the crank?

There's a reason a PS crank weighs close to 35 pounds.