If the whole rig of camera, lights, battery, is too heavy, it will throw off your balance/trim and make shooting video very difficult. Typical position is to hold the camera in front of your face so you can see what you are shooting. If the rig is too negative, it will make your trim tilt face down. Depending how heavy the "tank" battery canister is, you might want to consider wearing it separately on your waist. This is what I did when I used halogen lights and the big battery it required. What is the UW weight of the "tank" battery canister ? Sorry if it seems like I am taking over your thread. I know you didn't ask for my opinions, but I've gone through many of the situations you are describing and my experiences might help.The tank is heavy like hell, the spots should be fine Most likely I'll just use the tank as a base and attach the arms directly on it/maybe add a fin to make it swim smoother.