Last year (before the P2V was announced) I "spun" my phantom around so the battery door faces the back. That let me mount my gimbal even more forward so it sticks out the front and still maintains perfectly centered X-axis COG with a larger 4400-5400mah pack. This is great for me because it solves three problems - gets rid of COG issues, lets me really get the legs out of view even when shooting wide and moving fairly quickly on the sticks, and doesn't really impact the visual profile of the Phantom (nobody really even notices it's "backwards."
Other people have gone to similar lengths and more, including plasti-forming retrofits to the bottom shell to allow the battery to slide back further into the body. Others externally mount the batteries, which gives you a bit more sliding room as well.
Handling in the air is the same, you can't really tell in the air if something is front-heavy as long as the FC is doing its job maintaining attitude. It IS less prone to lurch on takeoff though, I can take off as slowly as I want and can even skit across the ground with the legs dragging on the floor. Zero difference in flight times, the Phantom is small enough where the front motors are not working that much harder to balance out a typically front-heavy craft.