justmyopinion expressed my own opinion.

Have you contacted an antique rug dealer, or a rug-cleaning service that specializes in antique rugs, to ask for their advice? They might have some useful insights.

Any area rug placed ATOP a wall to wall carpet, or any other rug for that matter, will bunch/crawl and not one thing on earth will prevent it, A rug belongs on a hard surface floor. You need a rubber back, felt pad created to your rug size at a good broadloom venue. NOT a big box store.

Is there another solution? No. It is akin to jamming a square peg into a round hole.

This week I purchased the Dura Hold plus rug pad from Rugistan. https://www.rugistan.com/products/durahold-plus-rug-pad-custom-cut

Recommended by Wirecutter, it is the best rug pad I have ever used. The bottom is grippy to my wood floor, and the top of the pad is felted in a way so the rug doesn't slide but stays put on the pad.

Rugistan customer service is excellent! I ordered online and the owner called me to verify the size of my actual rug knowing that antique rugs vary in size more than machined rugs. He wanted to hand cut the pad to match my specific rug measurements and account for a tiny overhang.

Bonus - they are on sale right now too.

I've had great success with Alien tape on the corners of my throw rugs and runners. It's worth a try.

^^^

"Grippy to my WOOD floor...

Exactly the type of pad I was referring to.

Thanks, everyone, for all the helpful suggestions! You're the best!

BEST rug pads I've found are at:

rugpadnation.com

Pricey, but worth it!

When I had that situation I used a rug pad with a sticky side stuck to the rug. The other side gripped the carpet. The Oriental rug still moved..but it didn't stretch out of shape.