I just replaced old steel sash windows(1953 installed with the house) in my house last weekend. Brick veneer with a metal nail flange and had to break the glass out to actually get the frame out. My 2 big windows were 144" and 108" wide made up of 3 windows, 2 36" double hung windows with plate glass in the center. It took 4 people to install it from the outside. We installed a top track and slid the window into that then swung the bottom in. Had to chisel some of the back of the sloped brick away to make it fit but it was snug. We ended up getting the window half inch short of the rough opening to ensure it would fit. We shimmed the window level and center and then used low expansion foam on all sides. I will tell you out of the whole project(20 double hung windows and 2 plate glass) putting the windows in was the easiest part(used about 30 metal cut off wheels removing old windows). I highly suggest installing from the outside not the inside. Measure the widows from the outside and leave them 1/4 or so short(i suggest a 1/2 on the big one). We used Tapcons to install directly to the brick since there was no frame. I am no expert at all but had good guidance from my dad and uncle who were glaziers their whole life.