My Stock battery is located under the rear passenger seat as it the perko switch. My Stereo Batteries are located under the front passenger compartment. Grant is correct the batteries weight 45lbs each. As far as extra ballast is concerned I have three 65lbs lead heads + a 20lb anchor in the nose, one 65lb brick hidden next to the passengers rear seat. One in the space behind the drivers throttle panel. Two 65lb bricks hidden next to the drivers side rear seats. I have one 65lb brick right behind the drivers seat that I can move around to balance the boat while in motion. I figured out everything including stock ballast, batteries, addtional lead ballast and my boat is balanced out very well. Probably 40/60 front to back. Very nice wake if I do say so myself. Here is a pic of my two stereo batteries.