When you punch to the body, it is best to get the shoulder of the side throwing the punch to the level of the target. If you know where to hit somebody and punch accurately, you can get a lot of value out of just a couple shots. Once you learn how to slip punches and close distance you can literally hit the body with very minimal risk.
Double jab with the second one setting up a right, get the opponent comfortable with you throwing the right up top enough that when you do the combo but drop the right down to the solar plexus it is completely unexpected, when you are throwing them up top be paying attention to their breathing, when you hit the solar plexus you want them to be as inflated as possible, really drop down into it like all of your weight is falling into it, ideally it's an overhand coming in/down at about a 45 degree angle
