What you can see in #67 is that the slope between the die, TIM and copper block is fairly fluent. As can be seen under the assumptions (#97) the thermal conductivity of normal TIM is ~0.01 x that of Cu.
So, from a non restricted heat transport point of view (perfect die contact and no heat dissipation limits) the TIM compound doesn’t influence the performance that much.
I’ve tested the use of AS3 versus the default goop versus no TIM (ah well, didn’t clean the die that well, just a tissue and some acetone) to evaluate the load behavior of the Vapochill PE (temperature on y-axis = CPU temperature). This time no calculations but measurements
