83' 70hp Evinrude Battery relocation

[bongo042]

She's been sitting about 10 years, been working on it about 6 months and its about 95% ready to get wet. I'm in the process of replacing the battery. One of the things I did was relocate the battery. I put this engine on a 1966 Lone Star boat and the engine seemed to weigh down the boat causing the bow to stick up a bit too high. To combat this I relocated the battery to the front. I fiberglassed a battery box with padding and a strap to secure it and ran high quality wiring to it. So far it doesnt have a problem starting it but I am concerned that the battery may not be able to stand the pounding and bouncing being in the front. My question is which battery would be best for this situation? I want something lightweight and can handle the bouncing and would like to keep it under $200 if possible. I would appreciate and thank in advance, anyone's input.