I missed an obvious video rig accessory when I bought the chest and shoulder rigs. I forgot quick release plates.
I grabbed a pair of Neewer ones, something they do well and cheaply and I know they will be compatible with my mechanical Gimbal and Tripod head plates (both Neewer). They do not line up perfectly with the Smallrig base plates, but are near enough and sit tightly.
I now have four head plates that are fully interchangeable with four accessories.
The big rig, probably only going to be used occasionally, but the handles might come in handy.
The matching Neewer quick release plates have joined the dots. They are a good size and cosmetic match, but the screws do not align perfectly. On the shoulder rig I managed to get two to align (just), but with the chest rig there is only one. Seems firm enough.
The Shoulder rig has some added weights from the Neewer Gimbal as I do not need the two heaviest ones. It just felt a little “floaty”, so the added heft anchors it better.
Possibly the LCD mount, but there are other options. The G9 has a top handle and a screen mount on the front of that.
The chest rig is simpler and most likely more often used as it is basically configured to aid how I actually shoot (hand held). I added the optional Ronin handle I bought a while back. This and the cameras own handle make a good balanced pair. Seems everything Smallrig ends up being useful.
There seems to be a red theme running through these accessories that matches the details on the Pana cameras. Irrelevant but nice.
All three video rigs have a plate, from the S5 in its cage, G9 in its and the universal Camvate one for the EM1x. There is a fourth plate for maybe the OSMO or the second G9.