I have used the hybrid design in my personal UQ's for years. I was one of the first few on HF to make a fractional diy UQ. I made a couple hybrid UQ's. I felt the synthetic insulation stayed in place on the sides and I used a wide chamber on the bottom for down. I had the idea to make a TQ that was similar. A hiking buddy was pestering Leigh to make him a TQ so we used him as a test dummy. After testing his we realized the design worked and came up with a lighter version for me that was still a solid 15* TQ. After using it at 2* with only a tshirt and underwear I felt that it was a design that Leigh could sell and know that most users would be warm at 15* and up.
The TQ has a 24" wide center section that is a karo quilt design that allows the quilt to loft a little higher than standard baffles. The sides have 2 layers of climashield designed to maximize the loft available. We could have gone with a thicker, single layer of climashield but from my experience a single layer varies in thickness. With the double layer we ensured that the loft was even without thin spots. The way Leigh sews in the two layers helps trap some air between the layers which helps maximize the climashield loft. (summer version only has 1 layer of climashield for warmer temps)
We feel that the climashield on the sides makes for a very consistent insulation that does not shift. Sometimes down will shift on the sides leaving a cold spot. When used with fractional UQ's I could feel the difference the climashield made when my feet would press against hammock. There is a loss of loft but the climashield still had some insulation value over compressed down.
I am not an engineer but from my experience the hybrid TQ "heats" up faster. This was something I noticed while testing. I don't have any technical facts to back this up so this is just an opinion.
We knew that this quilt would not be for everybody. Lots of vendors make great down quilts. Leigh's top quilt is an alternative choice. She can only sew a limited number of quilts so having a quilt that is not a mainstream choice is ok.
One of the things I like about her 15* top quilt is the way the quilt wraps the shoulder and keeps the quilt tucked in down the sides for back sleepers. This keeps a good seal and may be the difference in why the quilt performs so well in the low temps. It only takes one draft to lose a lot of heat. I find that in really cold temps I don't move as much and stay on my back most of the time. I think this a huge advantage if using on the ground, God forbid The summer version does not have the same shockcord system to help save weight and because you vent the quilt more in warm temps.
Rumor has it that if you just have to have an all down TQ they are available by special order. They are actually a lot quicker to make for Leigh.
Sorry to hijack the thread brushybill. Looking forward to your trip reports
Leigh's unpaid tech rep better known as "Dad"