Interesting. Thing is, I would like to make the entire arch with one board - thus an inverted "U". If I could accomplish this within a 36 - 40 inch opening, I figure the corner radiuses along the top corners would be to large. I figure that I wouldn't want a radius more than 6 - 9 inches. Might be able to accomplish with two boards at 90° radius with a tight splice at the very top. As you fellas can probably tell, I think everything through.

After working 10 hours a day and back home, you'd think I would have better things to do. Still have time to play with the puppies and read the news paper though.