I’ve had those covers cause more damage than they protect from. People, myself included, put those things on and forget to clean them regularly. So dirt and grit get trapped in there and cause the very scratches you’re trying to protect from.

For avoiding scratches, a “laptop sleeve” might be what you want. It can only used when transporting the laptop, though.

Normally, you just buy one for the screen size you have and that should fit well enough…

Are you more concerned about flex or scratches?

For scratches you really want something that adheres, like a skin. Anything else (like a phone case approach) will trap dust and dirt and simply grind it against the laptop.

For improving rigidity, I’d look into a 3D printed “case” for just the bottom half. I’d probably want ABS as it’s very rigid even when thin (though it’s been a while since I read up on current printing plastics).

If that case could be made to only have contact at the corners (so a tiny gap elsewhere) or fit over a skin, that could help prevent trapped dust from scratching.

This can be done, but will take quite a bit of effort, and won’t be cheap. Last 3d printing I had done for a phone dock cost me about $50, and I did the design work.

Once a friends’ mother gifted me a crochet 🧶 custom laptop case :)

3d printing sounds like the way to go, but there are plenty of services and individuals that can print for you.

You can order a 3D print from several websites. It is made up to your specifications, and shipped to you. It’s not even that expensive if it’s just a one time print and not a replacement for buying a 3D printer. They’ll make it however you want, you can even get one printed from literal titanium if you have the cash for it.

Aliexpress… Or if you can handle Chinese, Taobao.