Jerry, I thought I have purchased gray silnylon from OWFinc and it was much closer to a true gray…i.e. like the ID tarp in the background. But I have bought fabric from so many places that it is hard to keep track. I will try to look up what OWFinc gray color is. My tarp color is much closer to a brown with slight olive coloration. The photos on me website show the color better.
Tyler, The bivy design ended up being much more complicated then I had desired, but it was necessary to keep the weight down without feeling cramped. I'm traveling all week so don't have access to my notes, but will try to give details from memory.
The floor is indeed a bath tub design. Getting the bathtub at the foot end is easy. I pulled the corners in the way you do a square bottom stuff sack. The bivy width at the foot is 24". I pulled the corners sewing them to make a 6" high wall that is 18" wide. Just realize if you do this you loose 3" of length.
The bivy at its widest point is 36" where the zipper crosses the chest. The hood is sculpted by adding a "third" piece of fabric that was maybe 6" high at the top of the head and tapers to 0" where the zipper is and was about 36" long. It is sewn the full radius of the hood to the top and bottom pieces. This is hard to describe, but done correctly it adds volume to the hood and creates a bath tub floor.
I do want to say that I was influenced by MLD's super light bivy. I did not copy the bivy and in particular use a different approach to the hood area. I did study Ron's bivy and gained a tremendous appreciation for the design. It is not a simple as I first thought, his design details are a work of art.
All this being said you can greatly simplify this design by making the hood area square by taking the 36" width straight up to the top then using the same "stuff sack" squaring to give it a bath tub floor. You might add an ounce of material and not gain much in usable space. Quest has a bivy pattern that looks like it has the "square" hood.
Sorry this is probably confusing. If you have questions I am glad to keep answering until I am clear.
Jamie