If you remove the tank and put it in the back, the weight bias will not change as much as when the gas tank is in the front. Empty gas tanks don't weight that much, but a full tank does. If the front of the car being twitchy is your problem, I would check the alignment and or the tire size and the shocks that you are using.
Buggies are light in the front, but they have always been that way. It depends on how hard you want to hit the corners at. I don't think that the placement of the gas tank is going to affect the handling of the car that much....if it did, all cars would act funny when the tank is empty and handle better when the tank is full.
Sounds to me like someone is doing a bunch of bench racing, and gagging a nats, and swallowing camels.
I have a friend who has a kit car, and the gas tank is in the back with the motor, and the thing will cause you to be flug against the seat belts, when you corner.....and it will hang a corner at 45 mph (hard right or left) with no over or understeer, and absolutely scare the pshaw out of you.
It has nothing up front except the front beam. Suspension and alignment, ackerman, and roll center, these are the things that you need to be looking at!

If at first you don't succeed, beat the pshaw out of the business partner, and then go at it alone! LOL!