Pack (home-made and lightweight)

I've abandoned commercial packs as they are expensive (rip-offs) and unnecessarily heavy for most of my needs Day trips or 2-3 night so far. I'm 67 now and acknowledge weight-saving as a great benefit. Instead I have created two "NZ-made" packs using woven polyethylene? bags used for 15kg chicken feed (nicely illustrated) and 40kg English brewing malt which I found lying around. I line them with a rubbish bag. They are very tough. I use the old triangular attachment "bush pack" method of tying the straps with a stone in the inside bottom corners then tying-off the top. I use Mitre 10 poly 8mm rope inside a sleeve of soft plastic potable-water pipe which is then thread through some waterpipe insulation. If haven't had any discomfort or other serious issues. The hip belt is the same and I allow a bit of slack so that the lower portion of the pack is supported by it. It allows a ventilation gap for my sweaty back. I shove either a 3/4 or 1/4 length folded close-cell mat down the back for comfort. If you can handle the cruel jibes then it's great and (topical.) Weight? Under 500gms for the big 'un and 300 gms for the tiddler I estimate.