Two mates and I are conducting an expedition in August this year in South Australia. Essentially its 12.5 days and 625km, ~50km/day. Base gear weight excluding the actual pack is ~3.25kg, food ~12kg, water peaking usually at about 5L. This means at the start, pack weights will be around 21kg.
One Planet, an Australian Manufacturer of Rucksacks and Sleeping Bags have offered to modify/make a limited run of three modified Shadow Rucksacks for our expedition.
What we have to do, preferably in the next couple of weeks, is put together a package detailing what we want, and they will work out what similar spec fabrics they already have (from samples, etc) and what price they can do them for us as a Pro-deal. They will make the packs next time they do a production run of Shadows (hopefully before August...)
Essentially, what I want to do is mostly to the pack body. The harness is near perfect for these weights and activity levels...we already have these packs and have tested them extensively. They are basically perfect for our needs, we just want to trim the weight as much as possible, whilst still maintaining enough durability for minor Australian Scrub and the weights carried.
So, for the harness...
...changing the harness length adjustment buckle for something smaller and lighter webbing (this is more ergonomic)
...adding some extra, "stiffer" foam to the lumbar pad(ergonomic thing we have found again on long days-not normally a problem).
For the body (this is where I want your input)...
...changing back panel fabric to something with reasonable strength, but alot lighter than 500denier nylon. I am thinking something appx 4oz/square yard, like oxford pack cloth. 1.3oz silnylon is possibly too weak here (One Planet will only have to reinforce it for the harness...and we may end up using this pack for other expeditions with larger pack weights more like 30+kg, so I don't want seam failures), I was thinking 2.2oz silnylon, but again, will this be strong enough? Having a heavier fabric in this zone will help with scrub durability aswell (small amount expected, cf typical Aus conditions).
...Base, I am thinking the same fabric, in one piece from the back panel. We will be careful putting this pack down, and shouldnt have to "bum" our way over obstacles.
...Side panels of 2.2oz silnylon ripstop...I am pretty confident here that 2.2oz will be tear resistant enough for this application. Has anyone tested this weight material in North American Scrub? How does it fare?
...rear panel...this is the lightest panel on the standard Shadow, at 420denier (~6oz). I reckon this should probably be 1.3oz silnylon, or perhaps 0.97 thru-hiker spinnaker (if people think this is similarly durable-I am guessing it is from the feel of a sample I have).
...Lid...design left as standard (this will make it easier on their production line), but changed to same fabric as back/base panel. The lid sometimes cops a hammering in Aus bush.
...lid strap and buckle...changed to something really small and light. I am think a 1/2 inch buckle and webbing. The current one is complete overkill (its bigger than a standard UL pack's waist belt!)
...throat gusset/extendable throat...this pack currently doesn't have one, but I am thinking it would be handy...something simple made from either 1.3 silnylon or the 0.97 spinnaker.
...Compression Straps...I want to get them to incorporate a full compression lacing system, aka GG Mariposa. This is where I really need suggestions as to placement of loops, etc, from you guys. The current compression straps are complete overkill...there are 6 of them, not including the lid strap, and none of them are traditional base compression straps!
...Bottle Holders...mesh left as standard, fabric changed to same as back/bottom panel. The compression strap will be removed as we have found its not needed to keep the bottles in.
One Planet have been quite accomodating and helpful with this. They are a small company...probably almost the equivalent of a cottage manufacturer, and they make their gear in Melbourne Aus, whilst all other Aus manufacturers have gone off-shore. Hence, they don't normally sponsor people at all. They are willing to make these packs for us at pro-deal prices. They can't go insane with changing dimensions and things (this will cost them time and money on the prodcution line), but materials is something they can do, and simple things like the compression lacing system loops shouldnt be an issue.
My aim is to get the Shadow down to about 1.1kg, rather than the current ~1.6kg for the Long harness. One Planet think that the harness, including the current back panel (at ~8oz fabric) weighs just under a kilogram, so this will be tough.