mylar for tarp

I've slept a few nights under PolyCro tarp.
I don't sweat much under them but when my friend used it for 3 nights, his legs and sleeping bag were soaked.
Make sure you have a way of venting both on the bottom and top.

You can find stronger thicker versions of mylar, but will still be really weak and useless in the wind.
You have 2 poles for support and a bunch of different setup options that will all work.
Just go for the one you like and do it.
i would go with more of an A-Frame type that will give uniform pull on all corners.

Half the battle is the experimenting and reporting back to us how it goes from scratch to finish.

Are you talking about those cheap space blankets?
Those things won't hold up at all as a shelter. Maybe as an emergency shelter for a couple nights with no wind.
Also, they are super noisy. Ear plugs would be mandatory.
They do make those heavy duty space blankets with grommets, those make pretty good 5×7 tarps, very cheap and not super heavy considering the price. But there are lighter materials out there.

If the mylar has the slightest nick, it will tear on the dotted line. A space blanket can be used to waterproof a brush shelter, but that is a make-do emergency improvisation rather than a deliberate shelter choice.

There have been some successes with polycro heat-shrink window film:
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=59450

thank you all for the feedback. i planned on using it as an emergency tarp for my bivvy. most of my trips are 3 nights and under usually 2 so rain can be somewhat predicted beforehand. this emergency tarp would be for a surprise rain shower and i needed something to cook under and if i could'nt find a tree.

Al (George) Geist preferred the mylar over LDPE material but took the latter to Philmont because of the danger hail posed to mylar. I didn't even bother with mylar and started with LDPE and moved to polycryo as well. There was an extensive thread in the Philmont section on this and then a couple others on polycryo (one of which has already been pointed out). I was an active participant in all of them. For your purpose mylar may be fine as long as large hail isn't in the surprise thunderstorm.