I know, it’s crazy

Whoa! how have I not seen that bivy before? a question though on the size – how spacious is this thing? it says 33" wide, does that mean a 66" girth? If that's the case, it may be too small for me.

66" at the shoulders- what size is your sleeping bag? I don't put my pad inside so I have no problem.

hmmm my bag is 66 at the shoulders as well thats an interior measurement, so think that means that it would compress the loft and make me cold

It really doesn't compress anything, I have a 64" WM Megalite and I still have a very slight baggyness in the bivy. I'm 6'2" and 175- if that make a difference

Thanks again everyone for the great feedback! After sleeping on this, I think I know what I wanna do. My original idea of making my own silnylon would be a waste of time/money/frustration, but might work for the weekend. I can't get a hold of any tyvek (no construction projects around and lowe's won't sell me a short snip). The Equinox bivy looks interesting, but the more I look at it, the less I like it for longer than this trip, and so I feel like I'd be throwing $60 down the hole.

So here's what I got – a local store has some ripstop nylon on clearance for $3/yd and it's got DWR finish on it. I've got about 10 feet of 6 mil plastic sheeting in my basement collecting dust. I think I'll just take the plastic and make a bathtub floor, and get 2 yards of nylon to make a breathable top. I'll fasten it all together with super duper waterproof duct tape (http://www.lowes.com/lowes/lkn?action=productDetail&productId=256699-56131-178657&lpage=none).

Whattaya folks think? Will duct tape hold 'er together?

Not sure how that will hold up to being folded/rolled repeatedly with the foil backing. You may have better luck with Gorilla tape or 3M 2120.

If the duct tape doesn't hold, it would be really easy to sew it together by hand well enough to work for a short trip.

The 2120 doesn't appear to be waterproof. I'm not too concerned with the breakdown of the foil tape because it's only gonna be rolled up a few times (this is just for a weekend trip). I may not go with the foil tape in the end, but I think it has to be waterproof, able to handle cold temps (it could get to the teens), and of course, sticky as all get out.

Not a bad idea Walter – I may pick up some 2 mil plastic, hand sew, and seal with duct tape.

FWIW, I wouldn't use any of the plastic bivies as a shell for your sleeping bag. Using one outside your sleeping bag will lock all your sweat into the sleeping bag. They're VBLs. So if you want a wet bag, by all means… otherwise, stick with the Tyvek, some kind of breathable nylon, etc…

Brad – I'm only going to use plastic on the bottom, and use breathable nylon on the top. from a VBL standpoint, how is that different from using silnylon on bottom and nylon on top?

My comment was geared informationally toward the first mentions of nonbreathable bivies, for people who might read the thread and think that using those bivies by themselves as a primary outer shell would be fine. If you're hacking one up and using it underneath you, with a breathable top, that's fine.