I really hate to post this, especially considering how well thought out your post is....but you've got the cooling loop wrong. 
"Cold Loop"
On our NSX, the cooling loop starts at the water pump, which pumps cool water directly into the engine block. This water picks up heat from the cylinders, goes through the heads and exits via the two curved aluminum passages on the water distribution housing. When the thermostat is closed, most of this hot water is re-directed to the water pump via the coolant return pipe that sits on top of the engine block. This process ensures the engine will warm up quickly. You can see the path in the diagram below.
[ATTACH=full]197927[/ATTACH]
"Hot Loop"
If you examine the thermostat both in the diagram and inside the housing, you'll see that the thermowax pellet sits on the "hot" side of the housing and is bathed in the hot coolant that is coming off the heads/block. Once this coolant reaches 78C, the wax will start to (1) move the bypass plate away from the housing and (2) open the plunger on the cold side. By 90C the thermostat is fully open (10mm) and the radiator coolant loop is functioning. Instead of re-circulating into the engine block, the hot coolant is sent to the radiator. Returning cool water from the radiator enters the water distribution manifold via the thermo housing and is returned to the water pump via the return line on top of the engine block. As this cool water flows over the thermostat, the wax pellet will start to close until the temp reaches 78C again and then the whole cycle starts over. The water temperature in a normally-functioning NSX engine will fluctuate between 78C and 90C regardless of external conditions. See below.
[ATTACH=full]197926[/ATTACH]
If the water temperature goes over 90C, the thermostat will remain fully open and now you are relying on the Kcal/hour heat exchange capacity of the radiator to manage the water temperature of the system. If the heat in the coolant exceeds the cooling capacity of the radiator, the water temperature will continue to rise unless you either increase the cooling capacity of the radiator or reduce engine heat.
By hollowing out the thermostat you are deliberately creating a condition similar to a stuck thermostat, which on the NSX is always stuck open. This exposes the cold water to the radiator cooling loop immediately and you will find that the car warms up much more slowly and appears to have "better" cooling. However, eventually you will reach the thermal exchange capacity of the radiator and the water temp will continue to rise as along as engine heat exceeds capacity. It may also be that by increasing the opening size of the thermostat, you're increasing the flow rate of the coolant, which in theory might slightly improve the cooling capacity of the system. With the standard thermostat, the plunger opening is a relatively small "donut" shape and the return water is slowed when passing through the opening. Now with a big hole there, there is little restriction and more water can pass through the cooling loop in the same amount of time. However, you removed the thermostat and now the engine is not able to self-regulate its temperature. Instead, it will always go the equilibrium state of the radiator capacity. You may encounter issues with ring seal, emissions and AFR due to a cold engine block. Same with oil temp- you'll have cold oil in the system for a long time. Thus, I recommend returning the thermostat function to the system.
Virtually all NSX turbo systems use a significantly larger dual or triple pass radiator to drastically increase the Kcal/hour heat exchange capacity of the cooling system. The benefit of running this solution is that when the car is driven normally, the thermostat regulates the engine temp. But when you get into long periods of boost (like at the track), the big radiator takes over and keeps water temps down.
One potential improvement could be to keep your hollowed OEM thermostat for the flow benefit and fit a large-opening aftermarket thermostat into the "hot" feed side line of the radiator. This way, you maximize the coolant flow rate of the water pump, but keep the vital thermostat function for engine health.
