Don't underestimate the need to try it out.

In January, I got the Gregory Optic pack I mentioned previously. After alternating hikes between it and the Levity, I thought I had settled on the Levity. Early this week, I took an 8 mile hike with about 18 pounds in the Optic. That afternoon, I experienced weakness in my hips and back of my thighs, almost like a nerve had been pinched. (One thing I've never had is back pain.) This hadn't shown up on the previous 1 or 2 mile hikes around around the local walking track - it took a longer walk to trigger it. Turns out that the lumbar pad on the Gregory pack put pressure on just the wrong place, and sufficient time wearing the pack caused discomfort and weakness. (I had never had issues with lumbar pads on packs back in the 80s and 90s. Maybe, at age 70, I've lost just enough flexibility that it's now an issue?

I did some stretching for a few days, and it went away.

Yesterday, I loaded my Levity with about 18 pounds and took another 8 mile hike - no pain or discomfort. So, as much as I liked the design and overall suspension of the Optic, that one little quirk means the Gregory is out, and the Levity is back in. (I stopped by the local backpacking shop on my way home; they said they had a lot of people find the lumbar pads irritating to some degree or another.