The (disappointing) State of the Market in Lightweight Double wall tents….

To me the main problem would be that it is a very "niche" item, provably too small to justify the time and money required in develloping such an idea.
The basic design is possibly not that hard, however the "tinkering" needed to make it work is likely to be too much. A very basic obstacle is that if you design one for the needlessly tall people, normal folk like me would have the poncho looking like the bride's train. To make more than one size is not going to be an option.
On this point one needs to remember that when we spend a couple of days in the backyard tinkering, that is our "free" time, however if that is your job, it has to pay somehow.
Anyway some details at random.
Any multi-use item ends as a compromise.
If you are after a poncho that also becomes a "perfect" fly for a dedicated inner, you are bound to be disappointed.
But, taking into account some compromises, here are some comments.
The lightest fabrics/laminates at the moment (silnylon/Cuben/Spinnaker) are not breathable, therefore not the ideal rainwear material.
The breathable stuff is either heavier or not that waterproof.
To get that "dead air space" that a double wall tent should have , a poncho would be either too big or needs to be off the ground enough to annoy the ones that expect full wind rain protection .
One attempt was made by Michael Wong , at Luxe Outdoor, when he designed the Rocket that eventually morphed into the X-Rocket.
Made with lighter ( more expensive) materials could be light enough , but still a hiher risk that Luxe is prepared to take .
http://www.luxeoutdoor.com/eng/catalog-topic-gallery-view1.asp?id=821&selfpath=/12/125
For some reason I cannot find my pictures of this . I have tinkered with this, basically the changes from the first and second version, inspite of that I still prefer the Contrail and my Montane rain jacket.
Another problem I see is that if it starts to look like a solution to beginners , there is a high risk of having the forums flooded with negative comments from folk that will have problems with it. Keep in mind that even "experienced" hikers have problems setting up shelters like the Contrail or the Lunar Solo.
Obviously since we all have the exact same design, if one can do it , the problem is not with the shelters but that is hard to accept for some. See Ron Moak's comments on this point…
http://community.sixmoondesigns.com/blogs/ronmoak/archive/2008/07/01/lunar-solo-the-perfect-pitch.aspx

But that is just me.
Franco

When you say double wall, are you talking about mesh+fly or two solid layers (plus a bit of window)? I ask because the comment about melding the serenity with other largely mesh inners. mesh + fly I can think of at least 3 tents under 2;8 bigagnes seedhouse SL, Fly Creek UL, and MSR Carbon Reflex.
As well you can get four wall coverage shaped tarps + net tent for under 20 oz. pretty easily.

But it's only a matter of time before Roger comes in and states those are totally not double wall tents.

Otherwise I agree with Franco.

I think that Nate does have an interesting idea. As I understand it, he is saying that we are (almost) there already — that not a lot of development work would be required.

Lightweight combinations of a waterproof outer with a bug tent inner already exist and are on the market. All it would take is for someone to offer a version of the bug tent that replaces at least some of the bug netting with the lightest possible solid fabric (not much strength would be required).

The result would be a few ounces heavier than the pure netting version, but far lighter than existing double-walled tents. Sure, it is a niche product — aimed at the same niche that the existing bug tents are. How well it would compete would depend on its actual weight, and performance (such as whether experience shows it to be meaningfully warmer).

–MV

I haven't used it, but Habotai silk can be as light as 0.5 oz/square yard. Perhaps it would be suitable for an inner tent with the structure strength being provided by a silnylon or cuben outer tent. I'm assuming the inner tent hangs from the outer tent. Does anybody have any experience with this light silk?
Many years ago (1920s) very light silk tents were available for (13 oz without poles or stakes). They worked by being very tautly pitched. They would stretch when wet.
(Horace Kephart, Camping and Woodcraft, 1917). In this inner tent, it wouldn't need to be very taut, so stretching wouldn't be a problem.
–Walter

Yes Bob, you got it. Just thinking about how the Terra Nova tents create dead-air space with the inner-tent and how similar their design is to the current bug nets that are used in conjunctio with tarps and ponch-tarps. Seems to me that for a few more ounces, the bug nets could have a perimeter of lightweight fabric (momentum, silk, nylon, tyvek, whatever) and block drafts and add heat retention much like a double-wall tent.

That's the idea.

The x-rocket…wow. Thanks for pointing that out.

Interesting idea.

Just so there is no confusion, when I say “double walled tent”, the inner wall can be mesh or a less breathable fabric.

I’m a bit disappointed too, but I tend to want every option in a tent. Some of the problem is that the big manufacturers love to make double walled tents while the little tent makers make very few. Adding to the problem is the big tent makers refusal to make their tents out of silnylon (as noted in Will Reitveld’s excellent review of the new MSR tent) or Cuben (which is more understandable). Recently, I stumbled upon an event at REI, called “Tentapalooza”. They had several tents setup in a very big room. Many of the manufacturing reps were there (MSR, Black Diamond/Bibler, North Face, etc.). I was impressed with many of the designs, especially the pole configurations. However, the materials left something to be desired. The only single walled tent was the Black Diamond/Bibler, which uses breathable fabric. So, even though I was impressed with the designs, I really didn’t want to buy anything.

There is no shortage of creativity in the cottage tent industry, either. Ron and Henry are cranking out new designs every year, while Glen has gotten into the act as well. However, unless you count the bug bivy/tarp combination, there are very few double walled tents made out of silnylon, and none made out of Cuben (that I’m aware of). Personally, I would love to buy something like this: http://tinyurl.com/5ast55 (actually, I would like to buy something like that, but replace the side poles with trekking poles and have just one little pole on top). I would also love to have that X-Rocket in either Cuben or silnylon.