This is a tough question. I tried and tried to do the same thing anytime I get down to about 180, I have the last little bit in the middle of my belly.
I do South Beach quite a bit, and it seems to specifically help with the Belly fat. There are some complex biological interactions going on with fat storage, and there are many many factors that lead into the location of said storage. I don't know what they all are, but I do know that by doing a Phase 1 diet in South Beach (low, low carb, mostly complex carbs like raw almonds and green beans), I was able to get a little more toned in the mid-section.
Congrats on losing all of that weight, it will also firm up with time if you maintain the weight. There is a little lag period where the elasticity of the stomach has to rebound. I actually think I look worse after a few weeks of losing weight, because my body is not adapted to the new weight yet, but after a month or so of maintenance, it starts to tone up!