Is your belly fat visceral or subcutaneous? If the latter, it will sag further down as you increase its volume. If the former, the abdominal muscles enclosing that fat changes the belly shape into more of a sphere.
I have found that thru scientific experimentation, following diligent and careful study that the best results are achieved by eating. Eating a lot has proven to increase fat storage and thus a heavier belly. My is sticking out a lot, but beginning to droop a bit as it gets bigger.
Isn't it largely genetic? I mean a person's body will store fat, where it's going to store fat. For some people that's in the belly. Those types of people's bellies sag more. Someone who stores fat in the butt may have less belly sag.
One thing I've also noticed. If a person has always been fat--fat kid, fat teenager, fat adult--the body seems to ... get used to it somehow. Now obviously my study has been toward females, not males. But a fat woman who was a fat little girl tends to be rounder and firmer than a woman who was skinny all her life and then put on weight all of a sudden. Usually, those latter women are looser, saggier, with that sagging belly, rather than the spherical one.
Genetics also has something to do with it of course, as does lifestyle. If you were very active and athletic and then put on a lot of weight, you can still maintain something of your previous shape, albeit a lot more of that shape. For instance, I've known several women who were involved in weight lifting and other conditioning, and then, for whatever reason, slacked off on it and started munching more and staying away from the gyms. Their previously built muscle seemed to lift and support the fat, giving them thick, firm thighs without that jiggly, hanging fat that can be so fun to nibble, rounded tummies and fatter, wider shoulders.
Skeletal structure also comes into play. A smaller framed woman who did not work out as much who puts on a lot of weight, it kind of hangs off her. Rather than swelling out, her tummy kind of spreads around her and hangs down, because there's little muscle/skeletal structure to support it. In addition, the smaller boned people have a harder time being mobile with extra weight, because of those smaller skeletal structures.
So I don't think there's a magic answer to shaping your fat the way you want it. Genetics, lifestyle, previous life style, and body build all come into play.