Good points MTV, and I run across just that issue all the time. I often get longer rigging out just to reduce the compression loads on whatever it is I'm lifting. I also carry 3 different spreader bars, but often the choice is made to just use longer rigging, it's quicker and that saves my customer money. There is a way (and I should know it....) to calculate the compression loads when picking X amount of weight at different rigging angles. Point being, though using a spreader bar with vertical rigging is always the best, long enough rigging can ease that angle enough to reduce the comp loads to a point where it's "close enough." That's what I see in that pic of the bird being picked without a spreader, a nice shallow angle, (steep?) and I'd assume way below the stress point that the plane can handle with the usual flight loads. Nonetheless, your point is valid.
Back to crane/plane, and what the hell, e bike porn: here's a 100' by 100' red iron hanger just erected in Blackfoot that I did the initial crane work on. I was coming back from an out of town job that apparently also involved mountain biking, I overnighted the crane, hangared it, as I had a another job in the area the next day, and it saved me 40 miles of shuttling, at 5 MPG. That's a 1500 watt, 2 horsepower, 9 speed fat bike, with a 17 AH 52 volt Panasonic battery. It's pretty much the Back Country Cub with all the mods of e bikes

Since this picture was taken, I added the airplane cartoon in the crane cab rear window, so between the cartoon, the fat bike, if I'm carrying it, and the crane itself, I keep the traffic behind me amused.