With the addition of the NPF plate, the caddy is a little tougher to get in, but once its in - it's very tight.
The author remixed this model.
I took the awesome Atomos SSD caddy by @NassosT_72881 and added a dummy NPF mounting plate to it. Too many times I've wanted to mount my wireless transmitter to the back of the ninja, but couldn't figure out a good way until I found this SSD caddy.