Don't seem to use Z's as much any more around here, and except for loading the nose of one whose roller extension is gone, it's hard to see why you would need a stand in a trailer with flaps. But you also said you used the portable rollers, and if you knew what was meant (the roller segments which hook together or, after a little bit of wear, have to be overlapped) you would have to have loaded/unloaded flatbeds w/o using an extender. For my part I think it's easiest and safest to (carefully) tear a hole in the middle of a wall and establish an erosion channel rather than try to reverse-load, but that's sure not the Method.
The hole in the wall method is how i was taught to unload!
Now i'm getting "red cards" (don't know what the bloody hell those are) for not using anload stand. I think it's bull anyways, I'm 6'5" for crying outloud, i have to duck in drop frame trailers. In my experience, it takes longer (especially on certain doors whose hydraulic system is fading), takes up space, they're broken most of the time, I can reach the top of the walls in most trailers without one, and if a wall starts falling,(I'm looking at you CA Loaders!
), You're as good as injured. So why use them? I've had 4 sups (in a year) and this newest guy is the first to give me any crap about it, and he didn't for the first 3 months he was my supervisor. In my personal opinion, LOAD stands are for just that, loading.