Ended up making this bag instead. Been running it without a lid to date but probably should make one for my hunt in a couple weeks as I likely will need the capacity.
Adam is a great guy to work with. He patiently listened and corrected my errant thinking and we ended up with a simple and economical solution that works for me with the Eberlestock Mainframe load lifter issue. I'll post that on a different post under DIY. Great guy, honest, craftsman...