Got the axle all bolted together and attached, and had to stick my sweet junkyard-find wheels and tires (only $55!) on to see what it all looked like for the first time.

One more picture, just for fun.
I now need to take the u-bolts off and remove the axle and wheels again so I can finish painting it. The rims may need paint too at some point, but I think I'll go with a different color for some contrast. I might wait until the end to see what would look best.
The coupler I have is the bolt-on kind, so I will wait until later to fine tune my balance and bolt it on. The wheels are a little bigger than I originally had in mind, but I couldn't pass up the price. As it sits now, it's about 19" from ground to frame level, which could be a smidge high with a mattress inside, but we shall see. The tires are just snow tires with studs pulled out, so some smaller diameter, lower profile tires may be in my trailer's future. For now, though, she's a roller!
Jesse