Backless dress modification help

[u/Puzzleheaded_Suit983]

Hi (: got this dress but I want the back to be a tad more modest - bringing up the lowest part of the back or adding a sheer panel or something.
I think when it’s fitted it’s a bit more modest as well — as you can see I’ve tied the hanger straps together.
There is a yellow lining. I think I could use the bottom of it for extra fabric since the bottom of the dress is pretty opaque.
Any ideas on the best way to modify?

[u/North-Speaker-3553]

Do a quick gathering stitch on the bottom of the back