This is just as scary to me as the lumber stiff legs under the pickup photo .
I would never get under a suspended load, it should be resting on a safety or suspended again.
At the very minimum cut a piece of pipe in half lengthwise that will fit over the ram of the hydraulic cylinder & cut it to length that will rest on the head of the cylinder and the end of the ram where it attaches to the lift arm.
Then secure it with a couple of worm drive hose clamps so it cannot fall off. (Look at the cylinder blocking device on the lift arm of a skid steer loader).
Straps break, Chinese chain breaks, Chinese hooks straighten out. Cylinders bleed down, welds and fasteners break, in other words shit happens.
The wheels of the cherry picker are on gravel, not the slab, so the picker is less stable position than it should be.
I had a co worker die from that mistake, and a high school girl friends grandpa have his head crushed the same way, and a worker at our sister plant die because he didn't use the cylinder block arm on a skid steer , all 3 had hyd cylinder failures.
I am not trying to talk anyone down, I just do not want to have anyone get hurt or die due to being complacent or uninformed.
Please be safe.