You're welcome! Why would you move the horn? As I noted you will need to make a gasket to blend the horn to the cutout. High density open cell foam is preferred. Don't know if it's still available, but I use to buy trail pad at The Foam Store to make horn extensions to quell mouth reflections back to the throat and off nearby boundaries. Basically, a much larger, deeper variant of the M19's horn foam inset, though I didn't go out of my way to make such nice, tapered cuts.
GM