>>2472879By extending the bottom pieces for the waist belt, you get some space from those support bars on the sides and your shoulders. It minimizes contact points without changing the center of gravity too much.
You can see in your post with the Red Bag that even there, there is a center bar right smack dab in the center of the kidney pad, which tells me it is an important structural component even on frames with metal parts. I was trying to rack my brain to figure out a way to squeeze a pvc bracket or something to eliminate the center bar at the bottom but it doesn't make sense to given the purpose of the frame to be quick and easy to build, and the solution of putting either a straight bar or a running bend and just heating it over a heat source and bending it back to shape and give it some clearance suffices.
Originally, before that bottom piece you all see where the waist belt attaches, I attached the belt directly to the frame bottom when a center bar DID run through the middle, you had the pvc support beams press on your shoulders the whole time and it was uncomfortable.
>>2472873Exactly. The original idea for this frame was to have the waist belt attach directly to the center of the frame, and those enforced supports you put the blue area through was going to be a "reinforced shelf". It got in the way more than it was actually useful though so I switched over to the idea of adding a back shelf with no sides to hold onto equipment instead and it functioned much better.
As I wrote earlier, the reinforced area became the kidney belt piece. All of this was learned through trial and error which was my design process (
>>2472387) of actually going out and trying to design a decent PVC frame that wouldn't be too time or labor intensive to make.
>>2472882If I remember correctly last time I checked a 10' 1/2" Sch40 was about 5 bucks, which is almost double what you need to build the frame.
