I’m reading “Open” the autobiography of Andre Agassi. Andre is talking about his dad building a ball machine and aiming it at Andre’s feet forcing him to crowd the ball and hit it on the rise.
If you can improve this skill, you will take tons of time away from your fat opponents causing them to huff and puff even more and mishit all over the place.
Get yourself a ball machine or rent one and force yourself closer and closer to the point where the ball hits the court. Do forehands, backhands and half volleys till you start feeling more comfortable. I can guarantee you that your fat buddies are not doing this kind of practice. When you play them, they will wonder why they never have any time at all to get set up for your shots and you most likely will win handily.