sorry about the poor pic quality. my 2 meg "garage camera"
isn't like my 8 meg, but I don't have to resize to post directly.

progress
clear vinyl hose over the u-bolts
cleaned and painted the unistrut semi-gloss
1st box bolted down
the other polished door box came

this came out the way I wanted it.
the boxes look free-standing
are straight and level.
when you shake them you shake the trailer.
they move no more than the fenders going around town on some rough streets.
and that's with no wieght in them.
I am going to bend up a "skirt" to hide the butt ends of the struts, and mount an LED amber marker in.

don't really have a good pic but this one shows where I mean for the skirts.
some 1.5" aluminum bar stock bend it up and attach it to the stut. It's worth a try anyway...trim this deal out.
I want a better appearance, and a marker light about mid box, but won't drill holes in the box for it.

I cleaned the weatherstrip of aluminum chips and then wiped them down good with dielectric grease.

On to the coupler...

You are doing a great job, and giving me good ideas for my trailers.

Have you thought of using the space between the boxes, on the unitrack, to build a low storage area that is free-draining for items you don't want or need to put in the boxes. Items like wood blocks, wheel chocks, wet towels, etc?

That is a great idea. Another idea is to put the spare tires there. That is where I have always mounted them. They are still easy to get to when needed and it provides a nice clean look with them tucked in there out of sight. Here is a pic of our old Gladiator on the trailer as an example. No spare tires in sight.

yes, I have thought all along that will be used for something
if nothing else a couple of pieces of steel plate for jacking pinned through the holes...

or a steel wire "basket" for both a couple plates in the bottom and some blocks on top

or maybe even a low profile alum. box- maybe open with no lid, just bent up out of sheet? In terms of asthetics and keeping some bulky/heavy items captured in there...that's probably the direction I'll go.

I want to load the boat/get the boat on and examine the clearance before I brainstorm that one any further.

Thanks for the compliments guys.

power jacks...

Attwood and Barker always come to mind...

but I see refurbished Ultra-Fab 3500# on ebay for about $150 shipped.
with lights, hieght adjustable foot, and 18" stroke, full features...

Any thoughts?

door cables.

I was limited in location as I wanted to attach onto the latch studs to avoid drilling holes in the side of the doors
and I wanted then to go inside the box closed, and not cross the weatherstrip.

they would be hanging out the side all the time if I had them ouside.

they are primarily to keep the doors off the ground, though it feels pretty strong.