Yeah, I made two recently which I dubbed the 'pentamid' :) I made some cutting mistakes on the first one that I didn't notice until it was too late. The second and much better one is based on a 5x8 tarp pitched -mid fashion and while a bit cramped, is effective. I put 45mm catenary curves on the seams to give it a taut pitch. Unfortunately the curves rob it of some usable space, but otherwise it's a flappy mess.
Here's a pic from the rear; if you like I could take photos from other angles:
I've also got CAD drawings of shelter dimensions and pattern pieces, but I'm not sure about the ethics of posting such data for a shelter so strongly based on a commercial design.
I just discovered that those CAD drawings are on my laptop which I just killed and won't be getting to any time soon :|