Hey folks So I've got a fixer upper home that I'm currently reworking the bathroom of. The window faces to the front yard, and it's pretty obvious that glass block is the way to go. I'm going with the Pittsburgh-Corning pre-assembled vinyl-frame windows: (http://pittsburghcorning.com/files/...dential-products-lightwise-windows_gb-277.pdf). I'm thinking of going with the 40x40 size, and here's why: the measurements of the current window. I measured in three spots across the top and side. Top measurements are: 43, 43.0625, 43 Side measurements are: 45.625, 45.625, 45.5 The product sheet indicates that 40.9375" are required for the rough opening size. That's an inch or two off on either side, on all sides. How can I compensate for this? Any good videos online of this type of window replacement (youtube etc?) Thanks in advance.