Have been doing more experiments with images that are in the mid-size range, dimensions like 500 x 593, 490 x 768, and this is what I am finding:
The SVG wrapper helps to maintain the proper ratio; if only a height=100% or width=100% value is used, the one value causes the image to be uprezzed and the rest of the image is cut off.
I tried the max-height and max-width value; this distorted the images. Will try again in an SVG wrapper but will only set one max value and see if that works.
Any other suggestions greatly appreciated.Otherwise the default is to leave the images at their native dimensions and say to hell with it. In the dedicated readers and mobile device apps I tested,they all tended to do a much better job of downsizing images to fit when they are not in an SVG wrapper, and in the computer apps the downsampling is of such poor quality that the size issue becomes almost academic.