Thought I might share an inside look at how I went about this chop, you can see where the cuts were made. One thing I did wrong is the vertical window cuts should have been closer to the outside of the body. This would have eliminated the need for that filler piece at the lower corners. I did this once before and it lined up so well hardly any filler was needed except to smooth the sail panels.
The diagram below has been shared before but if you study the plan and follow the steps you'll be pleased with the results...