plexi glass case top back corner

Building a plexiglass case (the plexiglass is 3mm thick) for the Wanhao i3 Plus so created some corners and middle so far.
the holes in the plexiglass need to be 5mm just line up and drill hole.
the internal hole is smaller so the screw has something to grip on.

At the moment this is a work in progress and i will be adding the bottom pieces after as they will need to be different (i am considering either a magnetic front or hinges so once the rest is done ill look into one of them).
I am a