Yeah, probably why I won't do it! Though I wouldn't carry them on a daily basis. On this job I was getting close to the upper working load limit of my 2" slings, figuring 22,500 divided by 4, plus a bit of derating for the angle, (not to mention the out of balance loading of the container) which is why I went so long, to get a better rigging angle, to keep the loading down as much as possible on my 2" slings, as I guessed the load may be heavier than they figured. But they are also almost brand new so I wasn't too concerned. I used my 4 20' 3" slings on the bottom, the 2" on the top, (no reason for that) and would have preferred using 3" all around, again with the weight being an unknown, but I didn't have 8 of them.
I take my older rigging home, using it on my 40 acres, grossly abusing it doing stupid ranch stuff chores. Out in the sun, sharp angles, all the things we don't do for real. It is interesting and reassuring how tough the nylon slings are even after years of abuse, compared to how I baby my working rigging.
No purpose built container handlers in the area, the customer checked. Turns out the customer bought 80 acres, and will immediately start work on a house, plus he builds pole barns for a living, and I will now be his goto guy for all his hoisting needs. One problem though, he really wants a ride in the plane, I might be able to arrange that, especially if he keeps paying in cash.