Alot of anything on this game is genetics and sure you can do certain things to help but I can see my six pack even when at a 36 inch waste. I had one when I was 12 and never did any situps. Do heavy rope crunches, bicycle kicks and roman chair, those are the number one exercises on the EMG tests they do and adding weight will help bring out your ab muscles giving them a more pronounced look. I would also keep your reps at 15-20 and if you feel like you can do more reps you are not trying hard enough.