OK, go this measurements... waist 38, butt 42, length 22.

He's short and a bit chubby. With only a 4 inch difference between butt and waist I think I'll blow off tapering the pleats in the back and just build in curve at the sides by overlapping pleats a bit. That builds in a bit of taper int he sides and is quick and easy to do....that'll be fine.