I’ve modified my Jam as follows:
1. Cut out the foam backpanel and hydration bladder sleeve (and removed the foam backpanel).
-No real disadvantage as I didn’t use a hydration bladder in the sleeve since it caused a bulge along my back that was uncomfortable. I’ve used a 2L bladder in one of the side pockets and it works fine. Padding in the back was also unecessary since I put my sleeping pad along the back anyways.
2. Trimmed extra lengths of straps down on waistbelt, shoulder straps, etc.
-No disadvantages
3. Removed all the daisy chains except one, and also the ice axe loop and top holder on one side.
-No disadvantages, as I rarely used these at all. I kept the ice axe loop and top holder on one side in case I want to strap some trekking poles to the pack.
I can’t recall how much the pack weighed before, but after the mods my size M pack weighs 18 oz.
Dan