Never tried out Eagle, I do love my Kifura and ATS Raid (
the ATS made model not the Eagle). But I'm kinda old school despite my age, My main packs are a medium ALICE for April-Oct and a Large ALICE for Oct-April. Need that extra space for snivel gear/food. I'm a real big fan of the ALICE, it was my first pack so it's what I'm used to. Eagle does have a very good product behind the name, my only concern with the poster above who mentioned them making things for the .mil, .mil always goes for the lowest bidder or everyone would be issued Kifaru or MR. So I do hope their quality stays the same.
I found this on one of my frequent buyers sites, (mods if this is frowned upon please edit this out, just trying to help dude out)
Link To Eagle A111 on Clarence Link To Eagle A111 MOLLE (I don't work for the site, but I like sending business cus they've been very good to me).
Also HSGI makes bomb proof Sh*t, I have a HSGI Silverthrone, it's a vest but I believe they do make a pack or two, if not you could try a vest, I had surgery on my back and chest and needed something that distributed the weight better. Just a thought.
Hope your A111 or whatever you end up settling on is easy on your neck, trust me I feel your pain on having to buy 5-6 packs because of a medical issue. Good luck pal.