I've lost my camera, but here's my footage of the same session... :)
He crashed his quad not long after this video was taken. I had nothing to do with it, honest.
However, there are a couple of gotchas. The Core Pro as shipped with the Vendetta is 1.48 which doesn't have the PPM option. You'll need to use TBS Agent to upgrade the firmware to 1.51. You'll need to open up the Vendetta and connect the OSD to the PC via the USB port on the PCB next to where you fit the receiver.
I have it set up as channel 10 on my Taranis (which shows up as AUX 6 in Cleanflight) and via a mixer that's got a weight of 200 and an offset of -100 so the 0-100 RSSI value is translated to -100 to 100 PWM.
The next problem you'll encounter is the configuration wizard asks you to move the transmitter next to the quad for the maximum reading (which is displayed as about 82dB on the Taranis) and then turn off the taranis for the low reading and press enter. Of course, once you've turned off the transmitter, you can't operate the menus any more (and the physical enter button on the OSD doesn't seem to work in the wizard).
The solution is to temporarily drop the weight down to 0 and set the offset to 100 for the maximum which should give a PWM value around 2000:
You can then change the offset to -100 for the minimum value which should give a PWM value around 1000:
Finally, after confirming, you can then set the weight back to 200 and leave the offset to -100 and the RSSI value should match what you see on the taranis:
Happy flying! :)