I have not looked at a Precedent frame or the space under the body. The first thing you have to do is evaluate that, maybe even post some pictures.
The next thing to me is if I was undergoing such an effort I would first try to see if I could fit 8 6 volters, what the heck, once you are gutting a cart you might as well go for it
I am intrigued by such projects, so while at golf today, I will look for Precedents with 4 12 volt batteries and ask if I can look at the cart.
Love to know how you make out. I have CC DS undergoing some surgery as we speak to hold more batteries.