Hehe... from the (a mangled) Yahoo translation of that page, the text talks about 'if you don't want to pay $5 for the official Looney Labs cardboard set you can...".
Also note that you'd not use the base equilateral triangle in those patterns and, obviously, that they aren't giant, so you're still doing scaling... I guess it's easy to get Paint to do that for you, though.
Regarding JK's "MegaMids big enough to have a small ladder": you go! Though you MIGHT want to go with PVC and cloth construction, if you're going big enough to hide a body under them: thick enough cardboard for that job will get a bit heavy (think how it'd be to play with, say, refrigerator boxes).
Now I'm REALLY wanting to make Giant Mat Mids. I had the idea last night of cutting the camping mat such that the edges of each face interlock or "dovetail," using shapes like you set on the edges of snap-together foam floor panels. A whole Giant set could them be stored flat, to be snapped together on-site; and further, the "depth" of the interlocking dovetails would, themselves, provide stand-off (i.e. emulate wall thickness). Further STILL, such a pattern lets you get the most pieces out of a single camping mat, whereas a folding pattern is not very efficient when laid out on rectangular materials.