Grown up clothes

My other half selflessly piped up with “Something for me!” when I mumbled along the lines of “What shall I make next?”
Well, I’ve discovered he’s a difficult customer to sew for. I had to draft up a pattern based on Farbenmix Bo and they’ve ended up a little big around the waist.
Any suggestions on how to remedy this would be gratefully received. I’m considering adding some elastic around the back as that’s where it seems to gape.
Also I ran out of fabric and needed to get some extra for the waistband. As you can see it must have come from a different roll and is a slightly different colour. He never wears a tucked in shirt so it’s no biggy.

Apologies for the state of them – they were worn sailing yesterday and have been soaked in salt water before being carefully stored on the bedroom floor overnight. Don’t you just love ’em.

Pattern: Farbenmix Bo
Fabric: Spotlight Drill

Warmest,
Suzie