How old is your grandson?
If you look at him from the side, is his natural waistline parallel to the floor - or does it slope down in front?
This calls for an alterstion not found in many alteration books.
Backsides come as "flat, average, and rounded" - lok at the alterations for "full derriere" to get some more fabric in the area.
You might need to change brands to find a style that fits him better.
Last edited by bearisgray; 10-21-2017 at 04:07 AM.