Suparoo - More pics as requested, hope they are clear enough.
ScubyRoo - That is correct. The main beam is separate to the tow bar and had to be manufactured from scratch. It's the main load bearing and structural component in this contraption. Have a good squiz at one of the shots below, in the middle of the pic you can see the strap that comes off the main beam and is bolted with a high tensile bolt into an existing tow bar bolt hole/nut. This is only really there to stop the main beam trying to twist itself off the mounts that go into the chassis rails, not a load bearing component. You can also see a bit of the stitching of the original bumper reo where it was welded onto the main beam.
RSR555 - Let me know when you're ready to build and I'll give you some lengths as well ( have to go out with a tape measure).
Long and short of it is the majority is made from 2mm wall thickness box sections like 50x50 for the swingarms and the little box sections on the end of the main beam, the two pieces that come off the spare tyre upright and are welded onto the triangular plate which has 3 high tensile bolts onto which the spare is secured.The main beam was 50x75, 20x50 for the jerry can uprights, 50x8 plate for the tow bar mount straps, and sections of 50x5 plate for the ends of the swingarms where the fastener latches and securing pins are. The securing pins are 20mm solid lengths which are welded to a couple of box sections attached to the main beam to bring them out more or less to be inline with the plastic bumper.
Used a sheet of plate to mount the jerry can holder on and then a piece of 20x50 box cut diagonally to make to triangular gussets to support the holder as it is mounted right on the edge of the swingarm.
A couple pieces of angle were used to weld the nuts for the gas struts on the beam in a position as far out to the edge of the plastic bar as possible. 2 more nuts were welded onto the underside edge of the swignarms, as close as possible to the the tailgate. Very important to get the angles and measurements right for this. When closing the swingarms, the gas strut is compressed fully a bit before the swingarm arrives at its fully closed position. During the last few degrees of travel the strut actually lengthens a bit, therefore assisting in shutting the swingarm. It also means the arm doesn't swing out violently when the securing latch is detached.
The gas struts are a GG Mazda 6 sedan boot lid struts. Perfect length for this application. The ball mounts for these I got from work too. You could probably source something similar elsewhere: wreckers? or your local Mazda dealer.
The hole saw played a big part as well as the air powered dremel, in carving out holes in the plastic and bumper reo and also to get a nice cut on the swingarms to fit the bearing hubs. The hubs a pretty solid and I looked at the clearance between the plate and securing 20mm pins there is oxygen all the way around the pin. I have been driving around without the R clips in and the latches hold well enough, but for serious off roading I think I'll stick them in.
There is a fair bit of rooting around in order to gut the bumper reo, cut holes in appropriate places, etc, but the end result is worth it. To get the chassis mounts right, you have to insert the main beam into the gutted reo and use the beam as a straight edge between the two upper corners on the vehicle side of the bumper reo and where that line intersects the mounts, cut them off (the reo and plastic bumpers are in fact curved not straight). A lot of measuring all the way! Make sure you get the vertical and horizontal measurements before you cut as these will determine the end result of whether you can actually close your tailgate over the plastic bumper and also give you enough clearance for the latch hooks as well.
The bought stub axles have a square base and the top of the square part was pretty much inline with the top of the main beam, but the outer bottom corner had to cut off to match the profile of the plastic bumper.
This should give you some idea, as I said, when you are ready to build let me know. Happy to help

Confucius say: always remember the 6 P's - Planning & Preparation Prevent Piss Poor Performance....