Quote:

I think it would be a smart move to limit packs to around 60lbs instead of 80

I believe KF posted about this subject at one time. He's in great shape, bushwhacks on a regular basis, so he knows of what he speaks.

If I understand right, you were trying to lift multiple items using my bow lifting tip?  Problem with this is as much about weight distribution/balance points as weight.
Before I had a dedicated food pack, I had a big waterproof duffel bag that I carried food/kitchen items in.
One time early on, I decided that since it was a very short portage, I would carry my gear pack as usual and take my food duffel and set across top of pack behind my head.
The duffel had 2 haul loops each end and that's what I was holding onto when I found out the hard-way about ignoring the rule about keeping your pack weight close to lower back/hips.
Even though I had no problem setting duffel across pack and could handle the weight, it set the balance ( tipping) point to high above my centerline. The duffel itself was heavier on one end than the other do to the way my food/cooking utensils were packed.
I hit a little slippery rocky patch and stepped down on one side to keep from falling. As soon as I stepped down the extra weight toppled me over. Fortunately, the duffel fell off and I ended up in the turtle position. Embarrassed at my own folly but unhurt.
When you rehab, try the bow trick with just a pack. I think it will feel way different than trying to lift multiple items which if I understand correctly is what you were doing?