First off, that is not me. The first one is Hans, the official PT test pilot. The second unit with the white trim is Fourteen. He was gracious enough to get off the unit, take some photos, and pass them on to us.
THIS is a video of me and my version of the PT Pucker!

This huge log is 27" in diameter at the narrow end, 37" in diameter at the wide end and 53" long. It was sitting in my back yard for a few years. I can't estimate the weight, but I can only budge one end a couple of inches with my 200+ pounds on the end of a 5 foot pry bar. I used the pallet forks, lifted it about 6 inches and backed up, which caused the right rear tire to come off the ground a few inches. I lowered it down to 1 inch off the ground and the tractor came back down. Took it away like this.
To answer your question about the stresses that it puts on the steering rams and the center pivot point... I just don't know, to be honest. If you think about it, the PT425 can lift 800 pounds (we think) close to the quick attach point, much less as you go out further from that point. Once you get tippy you have all the weight of the rear section on that pivot point. It really doesn't matter if the unit is really close to tipping or already tipping, there isn't going to be any more weight put onto the joint. So, if it is engineered to hold that amount of weight, it should hold it.
I do recall a few years ago someone had one of the parts of the center pivot break off. I believe they got a new joint from PT and welded it on. That is the only incidence of joint failure that I know of.