Oh - hang on - you mean to have the seams horizontal - sorry sorry - I was visualising vertical seams.

I make quite a few kilts with patterns that run along the length, so I cut the fabric selvage to selvage and join the pieces hiding the joins in the folds, and I must be stuck in that mode.

When I had a larger waistline I added the under apron in a different, toning material, when I was still using material from my stash and needed to make the most of it.

If you did that then you could use the material from the waist to make part of the under apron pleats and so 'stretch' what you have still further. That would be using the material turned 90 degrees, but it would be hidden most of the time.

Anne the Pleater