It's not that you want the added weight, but rather that you want the supply of C16 or VP Import only when you need it, instead of burning it all the time, including the 99% of time that the car would be better off running on pump gas (not to mention much less costly).
Steve is right. The couple of people I have spoken to that have a fuel cell state that a 5gal of C16/VP import lasts them several tankfulls of pump since the C16 comes on only at x psi. Even if you are driving to a meet or a race, 99% you are off boost. Lets say you drive 30 min each way to get to your meet to drag or street race. You do 4 15second pulls. Well out of 3600 seconds (60minx60sec) you have only been on boost for 60 seconds which is about 1%. Now if your drive is more or went out looking for a race and came back empy handed, that formual gets even worse. And at close to $600/barrel for C16 and even more for VP imports, i think its worth it.
If you are a weight saving natzi and want to take out the foam around your speakers, etc etc, then this is not for you. But when it allows you to have several hundred more HP (depending on your setup) at your disposal at all times when you need it, who cares about the extra weight. You can be as light as you want, but if you forgot to fill up with C16 and that liter bike pulls up, you are screwed.