Hmmmmm. . . . if Newton had earlier designs with tank up front but then changed, there must have been a reason.
My logic, and it applies to aircraft, and cars (mostly off road for me), is as the fuel burns off, the C/G changes. Where is this least or more effective. my experience with hydros and planes is that the more the forward the tank is, the more effect it has on fwd and aft C/G and that is a bad recipe for performance.
The closer you put the tank to C/G, the more consistent the craft will perform. As far as the car goes, it's a big challenge, not much option for tank location, but for boats and planes, the placement of the tank at C/G is more easily accomplished.
There is advantage to putting a tank at a location that can change C/G while racing. BUT, it's a special type of driver or pilot that can keep up with the change and avoid the inevitable crash or loss of a race. I personally like for the setup to not change at all during a race or flight because there are enough changing conditions to worry about.
Some day I will try a fuel cell aft of C/G, my theory is, a little flighty at start of race when weight is heavy and course is smoother, then as fuel burns off, boat gets lighter, course gets rougher, speeds get faster and C/G moves forward and . . . . . . . . . . . .?
I prefer Mr. Cathy's location because of his reasons and mine.