I'm hoping you stick with us and let us know what you think if nobody else chimes in. I'm 100% in love with my Venture 2300, to the point that I can't even imagine there's a better saddle pack out there, which makes me want the pro version; but the darn MR camo fire deals got me on a pop up. I hate the pop up but have to admit it's fine for the few instances that I could actually want to pack one out, given the price tag. That said I do want to offload the pop up at some point and upgrade to a pro 2300 but the thing I learned from the popup is the stiff hip belt stinks in a tree, which I worry about with the pro and is why I'm not in a rush to drop $500 on another pack that I don't really need.
I hate the belt setup on the Popup 28 and was going to return the pack the day it arrived. But I swapped-in a Seek Outside belt and it changed the pack entirely. I don't use the wings, just run the belt through the lumbar slot and connect the webbing to the shoulder straps.
I already had a Kuiu Pro 3600 and a Kifaru Duplex Lite w/ Stryker XL to compare to the Popup. I picked up an Exo belt too.
The Seek Outside belt is the most minimalist of the lot, the least rigid, and the most adjustable (4 belt straps instead of two for customizing pressure across the hips). I find it very comfortable.
Having changed belts, I've kept the Popup and use it with my LWCG .5 and sticks. They work together best, imo. Even though the Kifaru frame is the best at reducing felt load, for me, the setup wasn't as efficient with the .5 as was the Popup. I use the Kifaru pack with my saddle platforms and climbing platform and it's been awesome with those sets.
I think the Kuiu Pro suspension is nice. I liked the 3600 bag too. It's firmly in the middle in most areas, imo, but it does excel over the others in two areas: 1. lightweightness and 2. bag layout. I let my brother use it and he liked it so much it's now his.
I can't promise a different belt will be the ticket for you and your MR. I've been surprised by reviews others have shared about the Popup. Some say they really like the MR Belt, (I don't). Some say the lumbar pad is too big (I wish it was thicker). I suppose different body shapes and sizes have a lot to do about that. But for my shape and size, getting rid of the MR belt made an enormous difference in overall pack comfort and performance. It's been a good little system for me.
I'd still like to try a Seek Outside Revolution frame. It's the lightest, and has the most adaptable load system by far. But I don't know how well the wide metal frame will do with a treestand cinched against it. The Stone Glacier frame with a flat back looks like an excellent stand carrier, no experience there either. I like a lot about the K4 design, but I don't like some things about load attachment. I'll have to see a bit more there. It is designed more like a Kifaru frame, but retaining some of what makes the K3 a bit cushier under light loads.
