I've been through the wringer on this subject. I purchased an !njoy Carlife unit, never received it.
I then purchased the I.L. Motorsports unit that's pretty much identical to the Thompson unit. It doesn't fit worth a damn. I had to "shim" the hell out of it with cardboard chunks and it looks terrible. REALLY irritates me that something as common as an NB Miata would result in two strikeouts for a part this simple.
There's no "cage" or anything that should be behind the console trim piece, right? Previous owner installed a single DIN stereo with a Metra install kit.
Removing all that for the I.L Motorsport install gave me this. Anything missing? I don't think there is.
Here you can see how crappy it fits side to side:
There's enough play side to side that you can get this sort of angle on it. This creates rattling and falling out. I ended up sitting the radio in the bottom DIN, this panel in the top, and there was about an 1/8-1/4" gap between the top of the panel and the upper trim. Unacceptable.