Mind, you, you're going to have to taper the pleats, aren't you? I mean, he's smaller around the waist than he is around his rumpus, so you're going to have to make each pleat a little bit smaller at the waist than it is at the rumpus level...just like the over-apron is smaller at the waist than it is at the rumpus.

How much smaller?

that depends on how many pleats you have, and what the difference is between his half-rumpus measurement and his half-waist.

Take the difference between his half-rumpus and half-waist, and divide that by the number of pleats. That's' how much smaller each pleat needs to be at the waist, than it is at the rumpus.