Sounds good, at least you have the weight distribution concerns in your thought process. My father and I built a large wildland fire engine with an 800 gallon tank many years ago. When we got the tank placed at the front of the bed it it caused the front axle to be quite over weight. We ended up moving it back about 18" to take the weight off the front. It made a nice storage pocket in front of the tank but created all sorts of problems with the pump now overhanging the rear of the bed. With a lot of work we got everything to fit in a lot smaller space with no overhang but it wasn't the way we had originally planned it to look. Stay flexible in your planning, that will help when when you encounter problems. Where there's a will there's a way so I'm sure you'll come up with your way to make it work.
