Light Bushwhacker Pack ???

For $300 or less check these out

HMG (Hyperlight Mountain Gear) Packs – There are several options here. The Porter is one of the better load haulers for UL packs. Not very heavy and compresses down nicely for smaller loads.

Gossamer Gear Gorilla

Zimmerbuilt custom pack – I have one, if you want details let me know.

Exped Lighting 45 – I've been experimenting with the bigger 60 liter version. Looks like a good load hauler. Might be bigger then you really need.

Appreciate the information Luke,
Looks like the Exped Lightning 55 with it's improved hydration system would be ideal to fit my current needs…LOL
It appears to have the sleekness with no mesh on the outside to snag.
I'm in southern Cal, so the ventilation is important.
With lumbar problems, weight on the hips is important, though I'm not sure about the stay going up the backbone.
I wonder how the material would hold up to abrasion, especially on the bottom.One reason that I'm shying away from Cuban. My main concern with any lightweight material.
It seems that Zimmerbuilt could satisfy most of these requirements except the ventilation aspect and the weight on the hips requirement. I like that it is a smaller company and he does have a great reputation. I wonder if he could come up with something or maybe already has something that I didn't see?

I had the same need- wanted a light pack that could still be bushwhacked in. I opted for a used Granite Gear Vapor Trail. It has less bells and whistles than the current GG models, but I like that.

HMG uses probably the most bomber fabric available on a lightweight pack. It's inside your budget, so I would look very closely at the HMG Porter.

FWIW, I find mine to be excellent on all fronts.

Get a ULA pack and ask them to do a non-mesh zippered back pocket.
The ULA is a great bushwacking pack, the only issue is the mesh back pocket.
Great weight carrying ability for light weight.

I've only had it out for one good trip but so far the Exped has worked well. I have not noticed the stay in the middle at all. I didn't think about ventilation but I'd say its pretty good, probably as good as anything else short of an Osprey Exos (which doesn't satisfy your other requirements).

If keeping weight on your hips is a big deal then I'd say the Exped and HMG packs would be your best bets. I've talked more about the Exped because its the one I have but I think either one could work well for you.

If you go for the HMG pack they don't have load lifters. I don't consider this a big deal but it does mean you need to make sure you get the correct size pack.