But chances are, I'd be grading the seam allowances somehow, possibly cutting the hemp at the seam and binding the edge of it with the outer fabric if the outer fabric is sturdy enough to hold the seam.

That's what I wish I'd done. But I was thinking about normal sleeves, and that I'd need a seam allowance. I don't have that much time to work on this.

I have Saturday. I have to keep remembering Saturday...

The outer fabric, by itself, is not that sturdy. When I cartridge pleat, I have to make sure that I get the edge through the hemp as well.
Ah. Maybe that means that folding it is correct.