i have a full bolt in steel cage and it weighs about 60kg. so it would slow you down a bit. ive thought about takin mine out just to see what the difference in lap times would be. just so you have an idea, my best time at symmons is 1.05.6 with a fairly stock car, apart from the the FMIC, 3'' exhuast, race tyres, and its debatable as to what it weighs as ive pull things out but it prob still weighs the standard weight with the cage, and 1.02.7 at baskerville.
those times should drop now i have a boost control, but its hard to say by how much. if i can knock a second off at each track ill be happy. particually at basky as it will put me right at the pointy end of the field.