The official download file is 24 pages long to print 12 double-sided, standard-sized cards. Has anyone consolidated the images to not use quite so much paper?

You could download each image to your computer, add them to a Microsoft Word document, arrange them in the correct order, then print them out 6 per sheet double-sided. The size of a standard SWD card is roughly 2.4" x 3.45" (you could probably get away with 2.5" x 3.5"); in Word, after you insert the image, you can insert the exact measurements. I've forgotten how to do that, but you could probably either figure it out or look it up.