Hmm... that's nearly an extra 50 lbs of unsprung weights on just the two parts you mentioned. Which according to some people is the equivalent of over 200 lbs of sprung weight. :shocked:
I can only guess this is due to what clubfoot said... them looking for long term reliability... and/or it's accountants at work.
Maybe these issues will be taken care of with the IS-F/
R???
Still tho... generally speaking... would you care about the weight if the car performs amazing? The one car that comes to mind in this case is the Nissan GT-R. It's a relatively heavy car... but it out-performs everything in sight. There's a video from Autocar comparing the 911 GT3 and the Nissan GT-R... and although the GT-R was a few hundred pounds heavier... it still lapped faster than the 911 GT-3.