It isn't a kart - karts don't have full suspensions. It's just a stripped car.
The best thing about this is that the rear view shows how the fuel tank packages into the car.
The worst thing about this is that far too much was cut away in the front. Paco (and others) sell brackets to reinforce the structure from the firewall area to the front suspension towers; this thing not only doesn't have bracing... it doesn't even have the stock inner structural panel which has proven to be inadequate! It must be far too flexible. Of course one could add structure back in...
It's also useless in most real-world situations, having no fenders. A track-only Miata which has more drag and less structural integrity than a stock Miata, just to save weight? I suppose if you have a Miata with crappy (rusted, damaged, missing) exterior panels but a sound structure underneath, this might make sense.