Like I've mentioned elsewhere, I had no significant issues with the mainframe as it came and have used it a ton 3 or 4 years rucking, day hunting, backcountry hunting, hauled elk, mule deer, sheep...but I hate the load shelf deal - never ever used it to hold any weight and it prevented being able to sit with the pack on, bumped into stuff, just wasn't useful. That said, over the course of a few years I did swap out to a K4 belt (size large) because I would have to do some "hitching" with the Eberlestock belt and it really didn't wrap far enough around my pelvis. That really gave it a "set it and forget it" function able to go for long distances without any hitching, adjusting, etc. I set my shoulder straps at almost the lowest setting and for some reason for me, at 6' 5", gave me the best feel and some decent load lifter function which I know was a big beef alot of folks had with the mainframe.
When the Mod frame came out I was for sure gonna get it...then decided I had my Mainframe so dialed and comfortable I really didn't need it...then decided I really, really hated the metal loop load shelf deal...so I just did it and got a Mod frame to try out. For me, it's definitely not a game changer in terms of comfort or hauling loads - it really feels and functions the same as my main frame. The belt that came with it was way too small for me without any real "wrap" around my pelvis (I wear 36 waist FWIW) and under load the front of the belt felt almost like it was taking the weight and getting pulled back into my belly while the big lumbar pad felt like it was pressing too much into my back. I swapped to my K4 belt from my mainframe - its now a perfect feel both in front and with the lumbar pad! I really think Eberlestock should offer different hip belt sizes out of the gate - a one size fits all system is going to have alot of unhappy people IMO. Along similar lines, I think they need to offer up/down/side-side adjustment to the anchor loops on the shoulder straps - sure you can move the shoulder straps themselves up and down but the anchor point at the top never changes. In my case, especially when I tension the load lifters,it kind of creates a funny gap in the back and kind of feels just loose - I don't think it changes the load hauling in any way but feels like it opens the door for some load instability on the occasion you might need it at the shoulder level. I've done a couple 5+ mile rucks with the 30# sandbag and it really does feel and function great - I do think it offers a little more ventilation than the mainframe setup. I'm surprised with all the time and re-do's they report putting into the new design they didn't come up with ways for more individual adjustability...that seems like a real miss to me, especially at a price point near other frames that do offer more individual adjustability.
Soooo, I swapped out the belt to the K4 which I already had, ultimately I have the shoulder straps about as low on the velcro and angled slightly inward to get as narrow at the top as I could which seems to feel the best for me even at 6'5", I took the load sling off because I really don't like a bunch of straps and material flopping around. I molle'd the Eberlestock sustainment pouch up high just like on my Mainframe for a hydration bladder and I keep the load sling setup and 4 gatekeeper straps inside it for when I am going to need them. (oh, the plastic gatekeeper buckles with the new Mod pack suck - they're just a PIA to open/close/move around, the old ones with the metal clips are way better, easier, faster, etc so I thru those in and put the new plastic ones in my Mainframe pouch). I molled a large Eberlestock pouch to the bottom and it has my kill kit/licensce/tags/etc in it. A single large batwing with 1000cc capacity fits perfectly over all that for my day stuff.
So, kind of a disappointment in a few aspects and mixed review from me personally but I anticipate it's really going to work great...just like my mainframe has...and I am able to sit down comfortably wearing the Mod frame with a load on it which was one of my main gripes with the Mainframe - will be nice for taking breaks hauling heavy load or quick glassing session and not have to either just stand or take the pack off.
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