Installing windows in living room slide-out

First, be very sure of the side wall construction before starting. Do not do any cutting until you know the size of the window frame. Do the inside first using, as mention earlier, blue tape to lay it out. I would use a multi purpose tool with a toothed cutting blade to cut the hole on the inside. If there are no surprises, I would use a jig saw to cut the outside wall, from the inside. Trial fit the frame to make sure you have enough clearance to fit the window in and not bind it. Cut 2Xs to the with of the wall between the inside and outside skin. Hollow out the foam to the depth needed for the 2xs how ever you can. Once everything is cut and ready, use construction adhesive to glue the 2xs between the skins, and use clamps for at least 24 hours. Just install the windows and enjoy.