I test In-Head and Under-Plug CHT's for Vespas and Lambrettas so you don't have to

Any time people talk about Vespa or Lambretta Cylinder Head Temperatures, the first question I ask is, "Under-plug or in-head?" Today, I set out to empirically test my assumptions about the differences and answer the question, "Are in-head sensors worth the extra pain and effort (of tapping the head)?"