I modded an old Cooler Master case some years ago because it wasn't wide enough to mount modern heatsinks that use 120 mm fans. I cut out a big window area on the side panel with my Dremel tool and cutoff wheels. Once I had the window cut in the side panel, I got some 1" x 1" hardwood at Lowes and built a frame to fit the window I just cut, then went to a glass shop and got them to cut me a piece of 1/8" plexiglass the same size of the window. The edges of the plexi were a bit rough from the glass shop. which I smoothed out with a sanding block and sandpaper. I then drilled holes through the wood spacer, case side and plexi and used brass screws to put it all together. Last, I took a 120 mm fan grill and used that as a template to cut out a fan hole for a 120 mm fan on the plexi and mounted a fan on the door. Using the wood as a spacer, I gave myself another inch of room inside to mount taller heatsinks and actually came out looking pretty good.