I think cutting a large side window on the P180 is not a good idea. P180 may be good in everything but it sucks in cable management. So if you have a large side window like the one above, you will have a messy rig.

I suggest cutting a side window just the size of a ATX mobo so that you can only see the mobo from outside, and not all the mess and drive cages. Maybe you can make a "P" shape window that helps to showoff the mobo and the PSU.

A smaller side window also helps to lower vibration... a thicker acrylic at the side panel also can make the side panel more rigid.