hen saddle that stays put?

I made some hen saddles for my chickens in the hopes they'd protect them from rooster damage. Alas, I find that they frequently flip up and I spend a lot of time chasing hens around trying to adjust them so they cover their back. Even doing this multiple times a day, it seems that even when the saddles stay in place, the rooster's nails always end up under the edge of the saddles and the girls are still getting cuts. I'm a beginner at sewing and not very good at figuring out how I can alter things to make them fit better. Especially when I don't have a cooperative model to try things on, as is the case with the chickens. Has anyone had success getting hen saddles to stay put? A different design for one that works well? Or perhaps ideas about how to change this design to make it more effective?

This is the pattern I used:

The ideas for changes I have so far are to change the point where the elastic attaches so it is further back, hopefully holding down the saddle more effectively. I don't really know if this will lead it to being more uncomfortable where it sits on the wing and/or fall off completely. An elastic strap from one side to the other that would go underneath the hen to hold the sides down seems like it could work. Except I can imagine problems with it sliding around lots or possibly pressing on the crop. I need a hen mannequin so I don't have to stress the girls trying ideas! I'd prefer to modify the saddles I have, if possible. If there's a better design out there that works well, that would be great too.

Here is my chicken saddle pattern that I adapted from a pattern that I found online and doesn't require elastic.

The measurements are for my hylines and I had to adjust it a couple of times to ensure that it sat above the wings and far enough down to cover the tail.

There are two slits for the wings so the slits need to be long enough to gently ease the chicken's wings through the slits.

There is a wing protector cover that is stitched down the middle and across the top and around an inch down either side.

A friend gave me a stack of curtain fabric swatches that came from a furnishing shop.

The fabric is pure cotton and lovely and bright.

I used a machine to zig zag around the edges to stop them fraying but pinking shears would do the job or else blanket stitch all the edges. ⁰

Megan, thank you so much for sharing this! That design seems like it would work so much better at protecting the girls! I really like that it doesn't have elastic too, since it seems to pull in weird ways and I worry they'll manage to pick at and eat it. The saddles you made look lovely too!

Your timing is excellent, since I had tried my two ideas at modifying the existing saddles without any luck and was at a loss. When I added an elastic strap that went underneath, it did hold it down better. Her natural movements caused the whole saddle to shift forward and bunch up though, leaving some of her back exposed. Plus I imagine how awful too tight pants feel on me and imagine the snug elastic must've been equally uncomfortable pressing on her keel. Moving the position of the wing elastics further back was even worse, as it just made the saddle bunch up and not sit flat at all.

Thank you again!