Just one more idea for you, I recently made some boxer shorts for DGS with elastic waist. The elastic was stretched and sewn around the waist using 4 rows of stitching. Instructions said when finished, steam elastic with iron to shrink it back in shape and that really did work! Before the steam it looked kind of stretched out and pathetic! Not sure if that would help in your situation, but might be worth a try.
This is great advice I have heard of doing this and completely forgot it.
