My cantilever seatpost rack and some other panniers arrived, so I loaded the Loop:

With one pannier removed, you can see the seatpost cantilever rack with pannier frame sitting on the Loop's integrated frame rack for more support.
I wrapped the removable rack's bottom corner with black vinyl electrical tape to avoid scratching the Loop's paint. I will be holding them together at that point using little Velcro straps (not yet installed). Since the removable rack is high, there is no heel interference even with large panniers.

The Loop is now carrying 2 front panniers, 2 large rear panniers, a small tent stuffed between the vertical sides of the removable rack and resting on the built-in rack, and a sleeping back bungee-tied to the top of the removable rack. Instead of the sleeping bag, I've also attached a trunk bag to the top for more storage instead of camping equipment. When I fold and pack the bike in its traveling configuration, I will remove the cantilever rack so the seat can go all the way down. It has a quick-release clamp to the seat post. I'm trying to figure out where to pack the removable rack, either with the bike in the same cover with padding foam, or in my luggage bag with the panniers etc. I relocated the triangular tool bag because in the location shown in prior pictures I had slight heel contact. I loaded all of the panniers with mock cargo (clothing, camping equipment, etc.) and rode around the UCSC campus with it. The handling is not bad. I wish it had one more lower gear, below the 27 gear-inch #1 gear, but even with what it's got, it has a lower gear range than the other folding bikes I've compared with it, so I can get up some rather big hill climbs on the UCSC campus, sitting. I was actually able to stuff all of this into the Schwinn Loop bike bag and use it as my one piece of luggage that Amtrak allows as carry-on when you bring a folding bike onboard. Using straps, I was able to get the bag into the Amtrak carryon dimensions, barely.

So with this equipment, the Loop can carry what a full-size touring bike can carry, except not as many water bottles mounted to the frame. The extra bottles will have to go in pannier side pockets or maybe I can attach another quick-release clamp-on bottle cage somewhere without interfering with knees and feet. I"m thinking maybe on the seat post or downtube or one more on the handlebar or its stem.

I also have a small above-the-wheel rack that mounts to the brake mounts and mirror hole on the top of the fork, but I haven't tried to mount it yet. Not sure I want to use it on this bike.