I'd advise you to stop talking sense, Guzzimoto, but I really want to see 40 pages. Think it's possible to make them lose their minds even more thoroughly? Let's try . . .
The mass of the copper insert in the stock holder is so miniscule compared to the mass of the head that the time delay for it coming to the same temp as that of the mass (versus the tips of the fins) of the cylinder head that I doubt the lag is greater than 2 seconds, if even that. It conducts heat just as efficiently back to the head as from the head to the sensor tip. That's why they used copper, which is a very expensive material. Therefore, assuming good contact or thermo goo, the small mass of the sensor tip added on will delay it maybe another 2 seconds. It's a short-term transient difference that cannot cause a steady state fault like poor running when hot at idle. If this were what were causing it, after a few seconds, your idle would return to normal.
You're baying at the base of the wrong tree.