1) Put masking tape on the Luan over the cut mark to minimize the tear-out
2) Mark out the hole 30 1/4" by 15 1/4" on the masking tape.
3) Drill a half inch hole somewhere just inside the cut line.
4) Use a scroll saw with a coarse metal blade, orbital turned off, and go towards the cut line, then turn and go to a corner. Speed?
5) Radius the corners, and cut continuous around to the point where I first met the cut line.
6) Install the window!
I considered putting some spacer in between the skin and the interior Luan, but after talking with the factory installer, he says if I position the window between two uprights (1st and 3rd), as I plan to do, I won't need to do anything, since the window frame will span from one upright to the other, and there will be one upright (2nd) that was sawed off that will space the wall in the middle. There should be good structural integrity and no bending in of the wall by the frame. The window frame should tie the 2nd upright to the 1st and 3rd.
Any suggestions? Problems?

Gil