Quote:Vile it down after cutting it to size and use a cornerhook (I have no idea what those things are called in English ) anyhow a 90 degree bend around it and see if it lines up with the material.
If it does then it is a clean cut of course this requires the side from which you are measuring to be flat.
From expierience I can say that once you vile it down it will get good anyway as you are rubbing the vile in a straight line along the block.
If you are just gluing 4 pieces together you should have thick material as you don't wan't to not be able to polish away the line where the plastics are fused.
I also recommend you to have only 3 pieces glued together being the sides and the front so you can have a detachable back plate as lowering in the motherboard with no room to shove it around is a pain in the ass. (although it doesn't really matter if you ain't gonna replace the internals > ever.