Well, I tried to come up with another design for a "cocktail dress" for tomorrow's Smithson dinner, and haven't had any luck. I tried one design, but the fit was really off and I just don't have the energy or enthusiasm to figure out how to fix it.
So, the next solution is to shop in my own closet. Gowns from the past years are all going to be too formal, I think, unless I take the drastic step of shortening one of them. Which isn't out of the question, of course.
One possibility is this dress, which I made two years ago and jokingly call my "cocktail dress":
Here's a closeup of the fabric:
(Hmm... no idea why it's showing up sideways) It's a quilting cotton, so my concern would be that it's just too casual for a real cocktail party.
Another option is to take the Smithson gown from two years ago:
Shorten it to mid-calf level and maybe remove the sleeves. The funny thing is, this is the same pattern I used to make the "cocktail dress".