In my opinion your big bulging belly just begs for being deflated by a precise punch to your solar plexus. Ideally when you are bound and restrained such that you cannot double up or turn away.
Of course I would also try other punches such as a horizontal karate chop right across your stomach, or a swinging left hook to your liver using a big boxing glove almost half the size of your belly.
I would then compare how well each these punches would make your abs tense up, drive the air out of your lungs, and deflate your belly.

Damn Daddy, I wanna hit your belly so bad

OOOF! Me too!

I love your gut daddy

Thanks son, punch me in my big gut!

Of course, I wish I had this opportunity

Very nice, Daddy

Thanks son!

My favorite belly :)

Thanks bud!