I had it sandwiched between two layers of net, in the hoop, and as I stitched had to be careful to take up the strands of the net as I worked so that it would hold together when the fabric was washed out. This is hard to see as you work, and you have the impression of stitching through fabric, but have to remember it will vanish.
So here's the completed stitching, from a contour drawing of sedum in my yard, but simplified to allow for linen thread and split stitch, done over net, all of which don't work in very small details.
And here's the stitching after the Vilene is washed out! and it seems to have worked nicely.
The drawing washed away with the Vilene, and the stitching is all holding up just fine, net backing in place as hoped. I just submerged it all in cool water and rubbed gently to release the dissolving Vilene fabric. Worked a treat. Now I feel safe doing more. Especially since the hand dyed thread didn't lose any color in the washing.
People usually do machine embroidery with this sort of thing, using just the Vilene and doing enough stitches that they become a lacy fabric, but it suited my purpose better as a hand embroiderer to use the net. I'll cut away all the excess net before I mount the stitching on the hanging. I love transparency and this was a way to get it.
The black background is a cardigan, which I wear and use often when a small matt black background is called for in pix. Technical point there..
And thank you everyone who commented and emailed and generally offered very helpful thoughts and observations on the Big Doorway piece, all of which I'm seriously thinking about. This is a new departure for me, to actually ask for input, usually I plunge ahead and don't much listen until something is actually exhibited. But it doesn't hurt to learn a new skill, and this is a very new one.
I've found in the past that other artists just stared at my work with nothing to say, never knew whether this meant loved it, hated it, thought it was awful, wished they'd made it, so I gave up years ago on looking for input on works in progress. But that was that group, probably not the best context for me.
However, this is a new group and a new outlook, so thank you. And I see I've found here people who are generous and willing to make suggestions. Much appreciated. Now I can see the work differently and I can make a better approach to it.