I have been diving the Ultralight Plate since they came out. The plate utilizes two cam bands and I add an adjustable loop hanger under the top "sex bolt" or as some call them a barrel screw. The lower cam band goes through the plate and the upper cam band goes through a stiff piece of webbing that is essentally a built in STA. You do not need to add a metal STA. I suppose you could but there is really no point to doing so. The plate is quite stable.
It should be noted that these fabric travel plates are never going to be as stable as a metal plate like a VDH plate or Freedom Plate but they are much lighter and IMO more comfortable. They are intended for use with tanks that are not terribly negative such as the ubiquitous aluminum 80 or 63.
I do not rig my Oxy plates per the instructions. I add keepers at the attach points to lock the harness. I rig standard Hogarthian single piece harness. (

, I think I need some new cam bands, those are getting old) The plates rig out around 5 pounds depending upon the wing and hardware.
I am weight integrated. I use two cam band trim pouches and two QR dump pouches on my waist. It is important to install the cam band trim pouches such that they are tucked in tightly between the tank and the plate to add stability and keep the center of gravity and lift close.
Some people rig the Oxy plate with a speed harness with both sides points of the waist strap allowed to slide and some leave only one side loose. As I said, I fix mine at all four points with keepers.
The Oxy plate rigs light and travels well and is comfortable without a wet suit for tropical diving with a swimsuit and rash guard or wear a suit as preferred. BTW, I do have down in classified an aluminum VDH single tank plate. Being metal the VDH plate is more stable with negative tanks and slung pony bottles.
I have found my Oxy Plates to be comfortable and durable and enjoy using them for warm water and tropical travel. My three, one has a VDH 18# wing, one has a Oxy Mach V 18# wing, one has a VDH 23# wing and is my favorite. So much so I have for the time being temporarily retired my (rare) VDH metal plate and as I said, I have another nice VDH plate listed in classifieds.
Oh, in hundreds of dives, the only thing that has broken was the crotch strap attach ring which is Nylon. What happened is I was walking into the water (shore dive in Red Sea) and tripped and fell backwards hitting the bottom with my cylinder which shoved the tank upward to the limit of the crotch strap (ouchie) and then snapped the Nylon attach ring. This has actually happned on another of my rigs going into a pool, slipped, fell back on my rear end and popped that Nylon ring. I have since cut the plastic rings off and installed a stainless slotted ring for crotch strap attachment. Oh, one last thing, the Oxy UL Plate does quite well without a crotch strap, I should know

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One last thing, you might ask about why the harness makes a Vee at the top and tucks into the piece of webbing, why does it do that? Well, what that allows is shoulder strap length adjustment as long as you leave a little extra material in the harness.