David thanks for the info...
I must have missed that typo, the HDPE sheet is 1/16" thick, and has been designed to follow my spine from the lowest lumbar vertebra to just above my shoulder blades. Just below the scapulae (plural) its width is designed to fit between then becomes wider to create a y at shoulder height. Think of a modified Arclight frame from Dana Design, and you will be close to the overall idea. I will create my own dual density padding from the closed cell foam and neoprene. Estimated pack weight is optimistically 4lbs, but will hopefully be closer to 3lbs depending how much I shave off the frame.
I have an excel sheet that says about 2lbs 2oz with extra fabric for the seams, zippers, buckles, compressions straps, webbing, reinforcements, frame (including aluminum stays and HDPE sheet epoxied), and sewn weight. That is not including padding, shoulder straps, and a couple plastic ladder locks and heat shrink for certain polyester strap coverings. The predicted weight off the top of my head with the extra items added in is about 3lbs 5oz +/- 5oz leaning more towards the plus for the tolerance limits.
Disclaimer- I am not trying to be rude or confrontational, just blunt.
I also believe there is a point when gear can become too light, and that point is when it does not perform its duty to fully protect from the elements. That's just the eagle scout in me (1/100)... I know this is supposed to be a 'superlight' site, but in my experience, Murphy's law takes precedence.
Thanks for the interest I will post pictures as soon as possible,
P.S. I have a lot of funny stories of people not being prepared.