Like most things in life, having one probe in the collector area is a compromise. Its not 100% accurate but its close enough to be acceptable for daily driver people like us. "Driving by temperature" is a great way to maintain maximum efficiency.
If you're serious and willing to spend the dough, $400-600, there are several models of aviation pyrometers that have 4-6 inputs in a single gauge. Most can be set to automatically display the hottest cylinder and even have a high limit alert.