Used a RAM tablet mount. like this, and 3d-printed some new ending pieces to fit my Surface Pro 4.
There’s enough space to have the keyboard folded one the back, and all ports are accessible.
I just welded 2 pieces of steel together and fastened with one screw to the side.
It seems to sit tight enough.
As a bonus I can rest my hand on the side window opener, and push the AgOpenGPS icons at the lower half on the left side. (Autosteer on/off etc)
FreeCAD file is here: