A while back I took a stab at making a synthetic TQ using IX insulation. Recently I finished a second version of this which I think is even better.
The King Tut v2.0 is a double layer IX TQ which features 5 X 5 inch air pockets throughout. The pockets are created by sewing pleats into the IX.
The bottom layer which measures 48 X 80 inches has 9 longitudinal pleats that stand 1/4 inch high. The top layer measures 50 X 80 inches and 15 lateral pleats also standing 1/4 inch high. The two layers are assembled with the pleats facing each other. The difference in width between the two layers in combination with the facing pleats creates a loft effect.
The foot box is a simple draw-cord with cord-locks (optional) on the end with a 26 inch Velcro tape along the running edge. My feet are size 12, but with 48 inches of overall width I find that I have plenty of foot room. The rig is easy to vent simply by opening the end and/or releasing the Velcro.
The shell of the TQ is calendared 1.1 RS nylon. Together the two types of material hold a lot of air, in much the same way that down does (at a fraction of the cost). I find that contrary to what some have said, the IX compresses very well. And so far it has proven to be very durable.
I don't know for certain what the limits of the TQ are. I had v1.0 up on Mount Royal with the temperature at -8C with a IX UQ and was quite comfy inside my 4S Man Cave tarp. Also I have no idea how much it weighs, but my guess would be around 14-16 oz.
Have a peak at some of the pics. The last one shows the TQ in a stuff sack next to my knife (10 inches long) for size comparison.