Nice stuff, except maybe for the weight.
The spec sheet on the Spaceloft insulating blanket specs the weight at 9.4 lbs/ft³ for the blanket.
That works out to: 3'x3'x0.20"x9.4 == 1.41 lbs/yd²
So lets see, an under quilt equal in size to the JRB Mt Washington under quilt, 77"x42" comes out to:
77"x42"x0.20'x9.4 == 3.52 lbs
So an under quilt from the Spaceloft blanket is 3.52 lbs as compared to the Mt Washington 3 at 22 oz (1.375 lbs) or the Mt Washington 4 at 28 oz (1.75 lbs).
Don't think you will have many buyers.
Now if they had the same blanket at 0.10" thickness, then it would be 1.76 lbs, 28.15 oz which is comparable to the Mt Washington 4 in weight.
At 0.10" thickness, the R-value would be 1.03. How does that compare to other materials?