In the end, I opted for a different option.
Here's what I ended up doing:
I began ironing the fold back and pinning the quilt to a white jelly roll strip.
It's hard to see because I used white thread but here is a view from the back.
I stitched down the side of the quilt, carefully, to preserve the shape of the quilt. I used the smallest seam possible. I am hoping the slight extra bulk doesn't come back to haunt me.
Here is the final quilt top, ready for a quilt sandwhich. I plan to do some free motion experimenting with this one.