MYOG Backpack Suspension Questions

Russell, I don't think the plastic sheet will do you much good in the end, aside from keeping stuff from poking you in the back. I'd get rid of it, as framesheets are just a weight-inefficient way to facilitate weight transfer. If you want a bit more structure in the backpanel, a piece of stiffer closed cell foam (like the blue camping mats from Walmart) will do the job, be more flexible than plastic, and if you make it removable it is also multi-use.

A full wrap belt will transfer weight better than belt wings, but be heavier, more complex to make, and looking at your photos you might have a hard time figuring out a way to sew it on so there's minimal fabric slack. Depending on the weight you intend to carry and personal preference belt wings can be just fine.

cool thanks, that helps a ton in the confusion of choice. I think if I get rid of the internal bungee and cutting board, then sew both sides of the pipe sleeve to the back panel it will give a stretched surface to reinforce the hip belt too. I designed it so the lowest part of the pipe rides just above that large spine bone so it needs padding and more flex for sure, plus the cutting board looks like it will wear through the fabric due to the stretching inside.

with a pound off my base weight I'm shooting for this to carry my 8lb base and up to 20lb with food and water.
Thanks again

Have you taken a close look at the Osprey Exos series frames? They use some similar paradigms.

You might like what you find if you think about shaping the lower circular portion of the frame like a Pringles potato chip; give it a saddle shape. Make it convex to your body on the vertical axis (bulging in to the hollow of your lower back) and concave on the horizontal axis (wrapping around your pelvis and spine). You can accomplish this by using 2 layers of fabric on the front and the back of the frame hoop and pull each taut on the respective axis. This will give you a trampoline effect hugging your lower back and should require less padding for a comfy fit along w/ an air gap between you and the pack for protection from lumpy objects as well as ventilation. This is more or less what Osprey does, but I think they use tubular aluminum stays.

SMD uses some flexible frame materials that could be similar to PEX, but I haven’t gotten my hands on one. Here’s a review w/ a good internal image showing the frame.

Yup. Keep it under 30# and you can just use a foam pad as David says. That is exactly what I do, too. My typical base weight is between 8-11 pounds, depending. My food adds up to more, usually. Anywhere up to about 22-23 pounds for a three week trip. I often go for single weeks or maybe two weeks. This would be either 8 pounds for one week or 15 pounds for two weeks.