Didn't put pics of the base, just because I thought you've seen one, seen 'em all, (plus my rigging of straps and tie downs, and tarp looked a little ridiculous) but I will tomorrow once I get the sides up.
I'm going with this axle
Tires I'm still debating on, and I'm interested to know what you think.
Like I've mentioned before, I really like the look of Pentaflex's trailer, but, correct me if I'm wrong, I attribute a lot of the bouncing we saw in his videos to the increase in mass of the unsprung weight, the tires, so with that in mind, I think I'm going to stick to 205/75 16s which will also be kinder to my wallet. Down the road I may think of getting something specific for off road.
I foresee using this trailer mainly for camping, and long trips, not much trail running, so tire size and ground clearance won't be much of an issue, but who knows that may change one day, which is also the reasoning behind going with a 54" hub face axle, to have the flexibility of running sensible trailer tires on a regular, and maybe have a set for off road.
Sounds like a plan.
Your axle choice looks plenty stout. Make sure you get it without a bend in it. You will never put enough weight in your little trailer to flatten out the bend (especially on the axle you're looking at). Plus this way if you decide to swap out your suspension and put the axle above the springs you won't have to remount the spring mounts.
I think Pentaflex's trailer bounced not because of his tires but because the factory springs are too stiff. Mine was bouncy too - I think it's just a combination of overly stiff slipper springs, a short tongue, and the fact we put more bulk than weight in our little trailers (and maybe a little too much air in the tires). They need to be swapped out for some softer, longer springs with a shackle at one end. It's a bolt-on affair, and the write-up is on this forum. It should decrease the bounce (and raise your trailer up a tad).
Unlike passenger car tires, trailer tires are designed to be drug around be beat on stuff. I've got Loadstar Bias Ply ST 205/75D/15 load range C tires on 15x5" Dexstar rims on my trailer. These tires are rated at 1820 lbs - I'm pretty sure I'm not overloading them! I'm very happy with them. With the wider replacement axle I got (51.25" hub to hub) it provides a little more than an inch clearance between these tires' sidewalls and the side of the trailer. With your 54" axle, in addition to some 205's you should be able to easily mount some 225/75/15" (rated at 2150 lbs) or maybe even 235/75/15" tires on 15x6" trailer rims
(if you wanted to). Unlike factory Jeep rims (which are really tucked in), trailer rims have zero offset - there's the same amount sticking out as there is facing inwards. And they run around low $30's to low $40's per wheel for painted 15" steel trailer wheels. Stay away from the 14" wheels and tires - they're an odd size; stick with a 15" tire and rim.
I figure the wider and heavier the trailer tires are, the more drag they cause. Whether it's statistically significant I don't know. But I've got a four cylinder TJ, so anything I can do to decrease drag from the trailer I figure is a good thing. The axle and 205 tires on my trailer help keep it narrow (good for off-road), and I've still got thee more inches of clearance under my trailer's axle than I do under the pumpkin of my Jeep's Dana 44 (with 33" tires). And the 205 tire isn't so big that I can't mount it on the trailer as a spare.
For reference purposes (as usual; shop around for the best price):
(good reference for height/width of trailer tires)
(another good reference for height/width of trailer tires)
(205/75D/15" load range C mounted on 15" rims for $79.99)
(these are my 15x5" silver painted rims in case you're interested - I just didn't want white rims on my trailer so I paid a little extra for silver - goes nice against the black trailer - I believe they also sell them in black - may be special order)
Soapbox: get three tire/wheel combo's so you have a spare; and when you order your axle order a spare hub and bearing set (they're not expensive). Do you really want to leave your trailer with all your gear parked on the side of the road or trail while you try and track down a spare tire or set of bearings? On a weekend? Or have to leave someone with the trailer while you try and track down a spare tire or set of bearings? If you're taking your trailer camping chances are you're out away from civilization. Trailers are pretty simple things; if something is going to go wrong and stop forward progress, the vast majority of the time it's either a tire issue or a bearing issue - be prepared for both - keep your spare tire and bearings/hub with your trailer at all times.