</font><font color="blue" class="small">( I am a single tractor operation, and from the size of the dirt loads in some of these photos of the tandem axle, I am assuming you are using a second tractor for loading after you hook up the trailer. )</font>
Nope (although that would be nice :grin)..... I just flip the tongue jack down and run it out so it's supporting the weight of the trailer's tongue, unhook the hydraulic lines from the tractor, and pull the hitch pin in the drawbar .... and I'm off to load the trailer .... with the tractor that was pulling the trailer.
When the trailer is full I back up the tractor to it, lining up the hole in the tractor drawbar to the holes on the trailer tongue (which is actually very easy), set the brake, shutoff tractor, hop off, reconnect hydraulic lines, drop the hitch pin into the drawbar, flip the tongue jack up and I'm on my way.
</font><font color="blue" class="small">( Have any of you 'all tried loading the tandem this way? )</font>
Yes .... I have it done perhaps 20+ times, with heaping loads, exactly that way.
</font><font color="blue" class="small">( I am thinking I may be forced to buy the wagon version so I can load it while it's not hooked up. )</font>
Nope.
In addition to the advantage of the tandem trailer being easier to back up (versus a wagon) here's another advantage: because the trailer uses a tongue jack and is designed to place 15% of the load weight on the tongue, it functions somewhat like an anchor (although I wouldn't tempt fate, thinking it would hold a loaded trailer on any kind of an incline) .... so it is less inclined to roll than a wagon.
With a wagon you absolutely gotta chock the wheels or there is nothing stopping it from rolling off ... with the trailer I'd say it is far less likely using the tongue jack .... if you are on fairly level ground, you could probably get away without chocking the trailers wheels. I generally throw a 4 x 4 behind the wheels on whatever appears to the downslope side just for safety's sake.