Dee,
I tried that on a gown done in this design for myself and the ribbon didn't survive being sewn in at the edge and washed.
What I've done with my dresses and I don't think I mentioned this in the directions is found the 1/2 way mark on the front and back and tacked the ribbon. Then I gathered each side so that I was making it be gathered to 5 inches across. (2 1/2 from the center to each edge) and tacked it. This width worked for Madison (Size 5/6). If she needs her's adjusted next year I'll just untack the edges, make the dress wider and tack again.

Hope this helps.
Susan

Here is a link that might be useful:

Susan,
I was able to go visit my grandbaby this week and got to see her wear her new pillowcase dresses. She looked like a little angel in them. My daughter has gotten so many compliments from her friends who have seen Anna wear the sweet dresses. Thanks again for sharing. By the way, my mom did tack the middle and edges the way you said so the ribbon wouldn't come loose and Anna would soon be stepping out of her dress and streaking at church.

AHA! The old tack in the center trick! I shoulda known. LOL!!
Thanks for the tip Susan.

Dee (putting her elastic back in the drawer)

Dee,
You could just send that elastic right on over to my drawer since I've been using it like it's free lately! LOL. I've got to order some from cheap trims, before I have to go buy some more.

Rhonda,
So glad Anna is getting good use out of the dreses and not streaking!
Susan