For the upper tailgate, I wasn't too happy with the original sliding locks. I replaced them a while back with gas struts. They took a bit of thinking to find the correct length to suit both the lift, and the retracted position (they kinda hide between the tailgate and body when retracted, so had to be careful with dimensions, especially diameter). The struts were made up by McNaughtans in Smithfield (97 Long St
Smithfield NSW 2164, telephone (02) 96095122), who stock various lengths and fittings, and gas them up to whatever load you are after. I used a spring balance to check how much load the struts needed to support, and then divided by two (as there are two struts). Gotta be careful to do this with the upper tailgate still installed, and measure where the struts will act (not at the end of the tailgate). My struts are gassed up enough that they come up slightly quicker than a new car bonnet, but not quick enough to deliver an uppercut to the unsuspecting.

I used the original mounting point on the tailgate, with a normal eyebolt end to the strut. There is a slight bending load on the strut, but probably not enough to damage it. In hindsight, I probably should replace it with a ball fitting (McNaughtans stock them):

On the body end of the strut, I again used the original mounting point. A spacer is required to bring the end of the strut away from the body (I used some stainless instrument tube offcuts):

For the lower tailgate stays, my intention was to use the original "rattly rods" to hold it open horizontally. I'm still not sure if I'll use them though. What I would like to try is some PVC-coated stainless steel cable, with an eye bound in each end. Provided it looks OK, this might prevent the rattling issue. The two cables would be about 2' long each (I'll measure for exact length), either clear or red coated PVC. Prefer thin cable - say roughly 100kg load rating each.
Anyone know a friendly rigger/balcony builder who could make these up from offcuts? If not, I'll start calling around the rigging supply and ships chandler places.
Cheers,
Harv