Bolo (BTW, one of my favorite martial artists),
The current thinking, from all I have read, is that doing lots of ab work (with no resistance) is just cardio work in a different way. Unless your abs are very weak, which I doubt (unless you do no overhead lifting which tends to indirectly work your abdominals) you are not going to see any big change in abdominal fat unless you start burning lots of calories. The question is: Do you like doing lots of sits ups/crunches/leg raises? if so, then they will cause fat reduction. Other wise, just add more time doing some low level cardio: walking/light running/cycling/hiking/etc. while keeping your calorie intake constant.
Hope this helps.