What's the point? Just to save a few pounds?? You might be saving the equivalent of 4 gallons of gas. If that much weight is so important, go "racing" with half a tank and call it a day. Reducing battery capacity drastically in a modern car with a ton of current draw is insane. Paying a bunch of money to do it is *really* insane.
Like i mentioned before, this all depends on what you're trying to do. If you're trying to save as much weight possible for the 1/4 mile track and you've already done all the other little things, this makes sense to me. Most people that go to the track(myself included) are aware that fuel weighs 8lbs per gallon, we already go to the track with 1/4-1/2 tank of fuel. It's very easy to bring a spare gas can when you start running low... 30lbs is a decent amount of weight once you've exhausted all other options. Personally i would suggest reducing rotational mass over stationary because it will make that much more of a difference. I am actually dropping off my car next weekend for a prototype drag brake kit(if it can be done) it should be good for 80-90lbs on all 4 corners, it will make a huge difference to me. Also the ability to run even lighter 15" wheels is just icing on the cake.