buy the full system skip a few meals (or just put down the fork earlier at every meal, an all round improvement I think You'll find!!12lbs is a lot to cut down for less than the cost of 1 slipon. Plus it sounds better and looks better.
Only kidding it just seems like a lot of hassle to save a few lbs, I know its all about the power to weight ration but a couple of horses here and a couple of lbs there ?? unless you are cutting seconds off a lap time does it really matter? The main reason I did the full system was for the noise, I love a bike to sound throaty, a nice deep raspy sound, the extra bhp and losing a few lbs was just a bonus for me, each to their own I guess.