So I also use Binhex PlexPass container so this image is super helpful! What I am curious about is which script did you end up using as I see two different ones posted in the comments.
There's this one...
#!/bin/bash
mkdir /tmp/PlexRamScratch
chmod -R 777 /tmp/PlexRamScratch
mount -t tmpfs -o size=4g tmpfs /tmp/PlexRamScratch
And also this one...
#!/bin/bash
mkdir /tmp/PlexRamScratch
mount -t tmpfs -o size=4g tmpfs /tmp/PlexRamScratch