I have loaded lots of dry hay with the same basic style loader that is in the first picture. The loader needed to hang over the back of the wagon and the flat area where the material came off could be shoved up till it was straight with the rest of the angled bed and locked into place to make a tall load. By the time we were finished a load the man at the back would be picking up material directly from the loader bed, which by then would be at your feet, and throwing it uphill to the front of the wagon. As with most things there was skill involved with building a good load that was large and stable enough that it did not shed material while travelling to the barn, especially when making the last corner onto the ramp to the threshing floor. I think our barn was about average for the main door and when the load went through the front would always rub on the top of the door frame. Ours was last used about 1982 when the baler broke and there was only a load or so left to bring in that day. The best loads had a tramper who moved around packing the loose hay while staying out of the way of the next forkful of hay coming forward. The tramper soon learned where the next fork would be going or else you ate a lot of dusty hay from your larger brothers. When only one person was on the load you tramped while the loader was bringing up light amounts or yelled for the tractor driver to halt while you caught up. I went from tramping to driving to loading as I got older and was able to take a turn on the wagon. Hard hot dusty work but swimming never felt better than in haying season. This is the closest I could find on youtube to what we did. Substitute a W4 tractor for the horses and that could be me in the late 70s. Ignore the baling and such after the loading. These boys like to handle their hay a lot of times.
http://www.youtube.com/watch?v=c2mPnAjO ... re=related