I think that we should discuss this some more.
Gone Fishin: while I agree that it may make a difference, what I'm looking from you, is your pespective, the technical details of why an IHS should be used. Wether or not I know where you're coming from, is irrelevant.
Can you share your insight on the issue?
Zhentar: are those numbers (0.23 and 0.25) real or just an example?
No tester really, really wants to run a second batch, with another heater, with or without an IHS. It can involve, among other things, building another heater, applying a TIM as Intel does to the IHS, which we're not really in a position to reproduce (pending a source of the TIM material that Intel uses).
But we still have to have some kind of justification as to why we wouldn't do it, if we decide not to do it. We should also try to quantify the error, if any, that this decision is going to have.
The purpose of a test bench is to measure the performance, by reproducing, as possible, what a typical PC might put the block through.
One might even wonder if the block should be mounted sideways, versus "flat down".