Amazing! The 'hunting' bike people could go far with this design.You know what? I love that Surly, and I also built out a very strong mid-tail bike that I used before it. On the Surly, those are 2x138L panniers - actually big duffel bags with a QD super strong attachment mechanism - and I have had that bike loaded to over 560 lbs total system weight where I have to travel about 10 miles loaded like that. Even at 8 mph with that much weight down low on the sides its *quite* a handful.
But there's a totally different type of bike that makes loads like that almost irrelevant to handling. I would not have believed it if I hadn't experienced it. In Feb of 2021 I completed a build of a Bullitt cargo frontloader. On my first Costco run, I couldn't believe the handling. It was almost unaffected. The issue of momentum and inertia were of course there, but the bike was literally no different in handling.
This 'Long John' type of bike is common in Europe and they are notoriously loopy/flexible. But the Bullitt is the exception. Super strong and stiff, actually nimble. The only reason I am bringing this up is there are a couple of crazy Germans out of Berlin who are making plans available for low tech, 3rd world bike construction, and the version of this bike is made for all terrain. Its beefy as hell and runs two big hub motors in an awd configuration. You could take those plans and make a bike that changes your game entirely.
Check this out: