I just ordered a data doubler for a 15in MBP i5 2.53 I just got cheap as a left over at MicroCenter. I am also using a 240GB SSD. I plan to put a 500GB HDD in either the optical drive or the HDD bay, but how would my battery change? Also does it really matter where the HDD is? Dont most HDD's have a motion sensor built in now so the one in the MacBook is almost useless right?