Dennis, Your question is a good one. Actually there was a discussion in the Precision Ag Talk Group on Ag Online (http://www.agriculture.com/agtalk/Ag_Groups.html) about "Combine Dynamics" that discusses this subject. You might want to take a look at it.
Basically, the Start Delay is an estimate of how long you need to wait once the header is down until you start receiving good data. Stop Delay is how long after the head goes up until you stop receiving good data. Five seconds seems to be the average that we see people using. These settings tend to be not quite as critical since they will only affect the amount of data mapped at the ends of rows.
The Combine Delay is the amount of time it takes for grain to get from the header to the sensor. This time can vary widely depending on the type of combine that you're using. This number is more critical to your yield map since it will effect the entire yield map.
Does anybody else out there have any good suggestions?