I'll start by asking, Are you sure the Denali Pro ($460) won't fit? You're of medium height, and the "small" size of the Pro is meant to accommodate torsos from 16 to 17.5 inches. Yet it still has 6,200 cubic inches of capacity, placing it within your desired range. So, if you can make the Pro work, that would be great as it's an excellent pack with great suspension, thoughtful design, and tough construction.
Barring that, Dana Design's Astralplane ($469) in the extra small size will certainly fitit's designed for torsos down to 15 incheswhile still providing just over 6,000 cubic inches of cargo capacity and superb load-lugging capabilities. I should think the same bag in a small size, similar to the Denali Pro, would also work.
After those two, the list of potential, off-the-shelf packs gets moderately small. Lowe Alpine's Liberty 95 ($279) might fit, although it would be at the low end of your capacity range. Osprey's Crescent 110 ($460) also should fit in its smaller configuration, with plenty of capacity. Ditto for the Vortex 5800 ($445).
My advice, then, is to get yourself to a good outdoor shop that carries at least two of the above brands, ask who the best pack-fitter in the store is, and get to work. You're well within the range of standard sizing, so I'm supremely confident you can find a pack that fits.
And, I hope you have a great trip!
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