Yeah, it changes it 2% (2") on a 2500 pound car with a 102" wheelbase by moving it into the trunk. It's half that by moving it into the middle of the car.
On a typical 3600 pound 115" wheelbase tri5 it's about 1%. It might be something good to do, but the change is pretty small. If you're trying to optimize everything on race car, it's a move in the right direction. But certainly not the same as moving the engine back 10".