Thanks, John.

The native resolution of the program appears to be 72 dpi, or perhaps on this is what has been saved in the original picture, I ought to try a 300 dpi image and see what happens. 72 dip output is compensated by having a big height and width so you have the ratio to reach 300 dpi. If I upscaled to a size I might like to print, I'd probably go in and change some things for the resolution, so it doesn't look pixelated, but it could be done. In a large painting, the background texture automatically is less significant. Some programs manage their memory better than others. At times, when working large, I've had to tile my work and reassemble to print.