Yes, its possible to over-ab, under-back. I was just thinking that without fanatical training, like 600 situps a day, abs are pretty much always the weaker of the two amongst everyone.
Train your weakness. The stuff that you're good at, is already getting done. What I mean is that if you are good at bicep curls, and can do sets with 70 pounds dumbells, you're already good, and need to focus on the opposing muscles and movements.
For belly pounds, cardio mixed with strength training is good.