Aiming to own one of the "coolest" MX-5 in OZ...

[Fatty]

*dumb question warning*

could you add a 2nd thermostat into the pipe that mr starlet has drawn in red? do "inline" thermostats even exist? so if you got one that was rated at the same temp as your main thermostat.. they would open at the same time. or is there any reason why this would not work...

[Steampunk]

you can add a 2nd thermostat to a cooling system (and I know some much bigger/powerful cars have), and BEGi has an even more dedicated coolant re-route that does this.
You cannot add another thermostat onto the bypass tube that I have, or else you block about 95% of the coolant flow.

Take a standard MX-5 engine; the coolant flow on startup is 95% just round and round the engine, ie. radiator-waterpump-engine-heater core in-heater core out-waterpump-engine... and so on, only a little bit goes back through the radiator via the thermostat and top radiator hose.

Once the coolant heats up, the thermostat opens and lets more coolant to flow through the radiator.

The bypass tube that is connected to the heater core out does not go back into the water pump and thus if you put a thermostat inline, the coolant flow will be almost halted.

[hot rod]

Sounds good mate but be aware that running an engine on the cool side for the long term can lead to accelerated cylinder bore wear.

I would think that 85-95c would be a better operating range?