Thinkpad x280: Internal Keyboard Cover/External Keyboard Platform

Look for my other keyboard designs at https://thumbsupkeyboards.etsy.com/

Laptops keyboards are far from ideal.
I prefer to use an external mechanical split/ergonomic board with my Thinkpads.
The built-in keyboard gets in the way - to use the machine with external board I either have to push it far enough (which was not comfortable for my eyes) or to put the laptop on a stand (which is either not always handy). One of the solutions would be a Surface tablet but the kick-stand they use make them impossible to use on the laps and the usual laptop. So I need to improve my laptop.

This platform provides a very simple solution to my typing problems.
It covers the built-in keyboard, provides a stable platform for my external keyboard.
In pictures there are two options: Let's Split and AnnePro boards, both fit pretty well.
Dactyl-Manuform is yet to be tested, I expect it to hang over the edges a bit, should fit anyway.

The platform is merely a flat board with the ridges and rubber feet holding it in place.
The ridges reflect the grooves in the "island" type keyboard, provide sufficient clearance between the cover and the key tops. Hole in the middle leaves the touchstick cap free.
Rubber feet prevent the cover from sliding sideways and lift it just a bit to avoid mouse buttons.

The board is created for Lenovo Thikpad x280.
It may be good for other Thinkpad models with an identical keyboard.

The cover is split into two parts - merely because the printer I use can do 220x220mm max. I used a soldering iron with a worn/blunt tip to connect them. That seam is done from the bottom side only, to avoid the ugly stitches on the smooth top side. Not sure how it will work in the long run.
From other hand the halves could be left separate. The rubber feet should hold them in place just fine, and the dovetail joints would restrict the sideways movements.