I know what you mean about them sagging; to keep the box shape while hanging from one edge requires stiffeners which add weight.
I also used OS32s which managed that very well but were helped by the HDPE backing plate. Within reason (and as I say on the comparison page) I don't think weight in soft panniers is wasted if it adds up to durability. Even if the bag ends up heavier than the lightest alloy box, it's still much better to crash on or have fall on your leg.

One way I thought of helping Mags and similar hold their shape is to fit a plastic box 'liner' like a sawn-off 25L water jerrican, or whatever fits best.

soft bags
 

I have been looking at the Enduristan monsoon evo3 32 liter
I have pannier frames for Touratech Zega Pro aluminum boxes
My frames are symmetrical I reworked them and tucked in the exhaust with a Acrapovic muffler for my f700 my width is 38" with 38 liter Panniers
The Enduristan has a mounting system like no other but you need 18mm frames
for the bottom bag mounts, this problem is solved with my pannier frames
and being symmetrical is the bonus
I have watched a few videos of overlanders with fancy set ups for soft bags and they all work great but most are a pain in the butt to secure & release the bags, Enduristan are not , Mechanical on the bottom supports with 2 pins for security and a strap at the top easy peasy.
Another thing that is always overlooked is the soft pannier semi Support/Racks that many manufactures have come up with is that they suck
if you have to lift your bike You need something to grab onto a tube is preferable
stamped aluminum plates Humm! Just watch Ichy boots videos She has transported her Honda in boats, baskets and what ever Try and lift a bike with nothing to grab on to or trying to tie it down
Tubular frames win hands down
Lyndon Poskit AKA Enduristan is at the top of his game He has a Aerospace Background
Airplanes are light for a reason simply good robust engineering especially when it comes to attaching things

This comparison list gets periodically updated, fyi.
Last revision: January 2024.
https://adventure-motorcycling.com/a...-soft-baggage/

I agree.