Here's what I would do with the coordinating fabric, depending on the weight and assuming the weight of both fabrics is the same. I would sew the two fabrics together at the sides and bottom. Then I would turn the edges over the main fabric, folding the raw edge under and stitch. If the trim fabric is lighter weight, then I would sew it so that it completely wraps around the base fabris - meaning cut the base fabric the full size, then trim the edges.

I've sewn for forty years, but I also hack things together from time to time. The above suggestion might just be one of those times, so listen to others as well!ðÂÂÂ

The tension rod will be a problem because a tension rod does not exist that will hold up to the pulling.

1929Spanish - The fabrics are both about the same weight. I'd say a good medium weight. Maybe even heavy. I wanted to mention I'll be adding a liner. Then wondered if the trim should just go between the two. The window is only 29" wide so I'm thinking the trim shouldn't be anymore than say 1-1.5" wide. I'm not sure if I'm skilled enough to fold the raw edge under and stitch right since it's pretty thick.

It won't be a functioning shade so there won't be any pulling on the tension rod. I'd like the shade to cover 1/3 of the window.

I realized that even if I use the clip rings, I still need to attach them to something.

Maybe my faux hobbled roman shades would be helpful. I didn't trim the edges, but used straps I made out of coordinating fabric using stitch witchery. The way the fabric is sewn, each pleat hides the stitching from the pleat below. I did use velcro and a rod, but a tension rod would work. Depending on the fabric, the stitching may be more or less noticeable.

If you want to border the roman shade, I'd cut the shade to the finished size you want, leave it unhemmed, and then wrap in the contrast binding using mitered corners. Below is one method for making double mitered corners....

Here is a link that might be useful: Mitered binding

Thanks Annie for the pics and that video was very helpful! Everything I typed in when searching didn't bring up anything similar. And hair pins are a good idea!
I like the straps you made on yours with the coordinating fabric too. Did you hand stitch your pleats? Use rings?

I just may try the easy method of hanging and draping with multiple tension rods and see if I can make it work to my liking without messing with rings.

No hand stitching or rings....a single row of machine stitching holds the pleat in place. Since they aren't moving, there's no need to do rings. The flap from the pleat above hides the machine stitching...except on the top row, but it doesn't bother me and it blends in well enough. You may want to do rings on that top one instead, or blind stitch the shade so it doesn't show.

I can't remember where I found the instructions for doing this...it was either on line, or I spent a bunch of time in the library too looking at sewing books for ideas at that time.

Thanks for the clarification Annie. You know, I have a couple sewing books that might also be helpful for me to page through.