Is there such thing as a decent, two-walled tent for two people under 3lbs?

It has been pointed out many times before but…
If you find that you get water seeping through, just give the floor a coat of silicone, that will add two ounces or so of weight.
Mix about 3 parts of minerals spirit to 1 part of 100% silicone and paint the floor. That is it…
Easy way to mix :
http://video.yahoo.com/watch/7248563/18899600
Franco

Giving the floor a coat of silicone + mineral spirits works (I've done it), but adding 2oz pretty much negates the weight saved by going with silnylon in the first place. It also makes the inside of the tent hard to clean because the dust/dirt sticks and won't sweep out. It's not a big deal and I'm splitting hairs here, but I don't see the appeal in a silnylon floor over a 3oz heavier floor that is more durable and waterproof. If you do need to re-waterproof a silnylon floor, I would just coat the underside of the floor with silicone and then dab a bit on the underside of your sleeping pad to avoid sliding around inside the tent.

Franco I know there are things that can be done to mitigate the issue. For instance, you could also use a groundcloth for around the same weight penalty as coating the floor.

I just chimed in because there were people itt claiming the issue doesn't exist, or that with good site selection skills its moot, when I know for a fact that that's not entirely true all the time. (Although I do believe it's true the great majority of the time.)

That was just a suggestion.
I did that on a BD tent, never on my Tarptents. Had no need to do that.
Personally I would go the groundcloth way as that is a modular (layering) way . By that I mean that you can choose if you want to use it or not.
Franco