I found I could get the file to load by doubling the horizontal and vertical MAXSIZE parms in the kfm files from 1024 x 768
to 2048 x 1700. However, after loading the file, it still does not show. I get a blue circle with a diagonal bar through it instead of the image. The image is on the server, but not displaying...just the blank box and symbol.
I stripped down my website to bare walls...and reinstalled from scratch with Design Extender. The problems went away. It seems that there are some risks to using the extensions on an existing site, but it works as expected on a new build.