The elastic hunt ended in spandex. After a great tip on where to find 12 inch elastic, (Thanks imblebee.) I realized the gores measured almost 12 1/2 inches long, before adding any seam allowance. Only after going with the spandex back up did I see the comment about sewing pieces of elastic together, (Thanks again imblebee!) which I really wish I would have done. Very Herve Leger. Much nicer than than what I ended up with, though what I ended up with isn't horribly bad.
I made each gore two layers of spandex, and basted the layers together. I attached one side of the gore to the back of the corsetlet, seam allowance to the outside, trimmed, folded, and pressed just like the other flat felled seams. I pinned the folded edge in place, leaving the tail I patterned hanging out. The tail is there to give me something to work with, something to grip when when working on this finicky area.
I sewed 1/16 from the fold just like before to make a flat felled seam on one side of the gore. Then I pinned the back piece with the gore to the side piece and treated them as one piece. One long seam was sewn to attach them, then I trimmed the seam allowance on the one side.
After the usual folding and pressing I pinned like crazy to hold everything in place for the last pass.
And here is a close up of join.
Not bad at all. I should say it took me an entire day to sew both gores in. I had to psyche myself up before each step. Once, I realized I was actually pacing back and forth thinking about the sewing involved, and I'm normally not a pacer. Here's a shot of the corselet so far.
Hook and eye time!