Generally, steep ground and too much weight put an excessive pressures on the spine which can lead to multiple unpleasant consequences. "Imagine carrying an 8-year-old around your neck several hours per day" ( http://www.javad.com/jgnss/javad/news/pr20151229.html ). Luckily, LS will probably save you during measurement sessions.
Anyway, I will not hesitate to modify the J-Caddy (if I had one) to add some folding wheels to J-Pack (just my opinion)..
As a solo operator, I love my J-Pack. I didn't know when it was being developed if I would use it much or not. I use it on almost every job. I have just about everything I need:
Triumph-LS on rover pole (for when I'm running around on the atv).
heavy duty military folding shovel
3lb engineer's hammer
a handful of 60d nails with washers
two water bottles
half dozen rebar
tree borer (thanks @Steve Hankins)
And at times I've carried other things like snacks/lunch, wood stakes, markers, water filter, glasses.
It basically means I don't have to load the four wheeler. I've got it all together already. When I have to park the four wheeler and go on foot, I've still got it all together. I seldom ever have to go back to the truck to retrieve something that I forgot because it's always together. That's probably the number 1 hassle of being solo in the field is forgetting something and having to stop work to go get it instead of sending the help. The J-Pack reduces this by a significant amount.
Regarding weight. It'll carry more than I want. Once it's on the back, the weight is very well distributed and low. It's also not very thick so most of the weight is close to the body. It's a little difficult sometimes navigating through close brush. But it's tough enough that I just plow through. It definitely allows me to typically do my one-pass-through survey reducing return trips to a point.
I have one. It's pretty big.
I use an atv, 90% of the time.
It's tempting to over fill it, and make it too heavy.
But, I added a piece of 4" thinwall pvc to it, with a cap on the bottom. It's for rebar.
I need a better way to fasten it in, so the pvc does not flop around.
It's good. I wish it were a little smaller, and had a padded waist device, to put more weight on my hips.
Truth be told, I think I've overloaded mine!
I'll re pack, and consider what im carrying, and reply later.
I think it's pretty good, with room for improvement. It would be nice to have another strap across the chest to hold the shoulder straps together, and also a belt to keep the weight better distributed. It'll hold way more than you should be carrying, so be careful not to overload it. The velcro outside pockets are great, but they don't seal shut as well as I'd like. There's a chance smaller items could slip out. I'd say it doesn't need to be quite that big, but that's just a personal preference I guess. Overall I'd give it a B+.