Thanks so much for the suggestions. It is good to have a group that is not demeaning of oddball ideas.
Jorge, your suggestion gave me an idea I will try today. I bought a sheet of Plexiglas. I am going to cut it to the width of the filters I use. I will attempt to compose the scene on the GG, and then hold up the cut Plexiglas and look through it. No camera, and match the perspective I see on the GG. Take a sharpie pen and outline the contour of the horizon. With this as a template, I can then cut the cardboard to match. This might produce more accurate results than just trial and error. I will report on the trial latter.
Thanks again for the suggestions and the positive tone of the site.