It's only an oz or two difference in weight. The arc looks pretty substantial to me:
flex-air-flow-back-panel.jpg
AT: 695.7 mi
Benton MacKaye Trail '20
Pinhoti Trail '18-19'
@leonidasonthetrail https://www.youtube.com/c/LeonidasontheTrail
I came across the Marmot Graviton 38 and 58L on sale for $119 on Massdrop that might be worth taking a look at, and it looks like it also has a lot of back breathability with the mesh and arc. It's slightly heavier than the SMD Fusion 50L though, but only $20 more expensive.
Actually since you're interested in the 38L Exos the 38L Graviton comes in at 38oz. And it's $129 until the lowest price is unlocked:
https://www.massdrop.com/buy/marmot-graviton
AT: 695.7 mi
Benton MacKaye Trail '20
Pinhoti Trail '18-19'
@leonidasonthetrail https://www.youtube.com/c/LeonidasontheTrail
The Granite Gear Crown V.C. 60 has ventilation channels molded into the back. I think the "V.C." stands for "vapor current". 34 ounces.
AT: 695.7 mi
Benton MacKaye Trail '20
Pinhoti Trail '18-19'
@leonidasonthetrail https://www.youtube.com/c/LeonidasontheTrail
It's also worth noting what the least-liked items were in the PCT survey. Sometimes the same item (e.g., ULA Circuit) shows up on both "most liked" and "least liked" lists, presumably because it is used by so many people. So, in some cases, you don't get a sense of the rate of like/dislike, just a count. (true with real life anecdotes, too)
http://www.halfwayanywhere.com/trail...ey-gear-guide/
FWIW an Osprey pack (but not the Exos) was on the least-liked list.
JC, if you're go to pack volume is 40L or slightly less have you explored frameless packs? It would be up to user ability but some frameless pack users have been able to bend the pack horizontally and/or vertically via packing or virtual frame sheet configurations to have much less material in contact with your back.
What we're observing in Mac's survey is an increase in less advanced or less experienced, hence lesser evolved kits/heavier kits, than yrs previous to the exponential increase in PCT usage... DESPITE UL gear advancement NOTING SHARPLY THAT UL PHILOSOPHY IS NOT JUST ABOUT BUYING UL GEAR! It used to be - pre 2012 - the packs listed in Mac's survey would be excessively voluminous for PCT thrus or less commonly used. The face of PCT thrus is/has changing/changed with the increased popularity of first time or less experienced hikers attempting teh PCT as their first really long distance hike or doing long section hikes.
IMHO, the ULA Circuit and ULA catalyst(a large volume pack not typical for PCT thrus pre 2012) was liked/disliked not because of their popularity but because both are hotter more cumbersome larger backpacks to use with no space between the pack and a user's back. Lugging a large volume 70 L + pack through a HOT Mojave Desert has often been vastly unnecessarily for PCT thrus pre 2012 who tended to be more trail savvy experienced. It's why packs with a spacer mesh backs like ZPacks Arc Blast and Osprey's Exos 48 L and Atmos 48 L have been PCT favorites for quite a while.
I have the Exos 58 and love it. Not only is the back as cool as it can be, the trampoline also gives great support over your whole back. The belt and straps are pretty weak, so I added some 1/4" closed cell foam to beef them up a bit. It seems like the belt is built with that in mind. I've never seen another one designed like that. I normally carry about 26 ilbs and love it when it gets to 20 ish! After a few days of food are gone. So, I can't recommend the Exos series highly enough.