I made a couple and they work pretty good from what we've tested. I took a 4' x 8' piece of light camo material, and than sewed straps 4" apart going vertically in it. So in the end it's basically a big, natural vegatation blanket after you stuff the straps with vegatation. I have a 4'x1' opening for the eyes, and a velcroed(sp.?) opening for my body to pop out of.
All four corners are staked down, and if you can get permission, dig shallow pits(about 6" is enough). From there I have a padded, swivel recliner that's comforable. And with all of this, you're no more than 6" or so off of the plane of the ground. So it casts virtually no shadow.
I made two of them, and I'll bring them out to the member's hunt this spring(I know you'll be there) and you can check it out, and I'll take some pictures and put them on.