Let's assume there is a certified course with a couple of certified distance points on it. At various points along the course, there are opportunities for adding distance by means of a loop of some sort. Further, it is the lucky case that a certified point happens to be the point where an out and back could be inserted.
The question: would it be appropriate, allowed, or even reasonable, to properly measure the course addendum and use the combination of new measurement and the existing certification (data) as the basis for a new certification, without the need to remeasure the existing certified course?
The rationale: I'm about to measure a very long course and the base loop of it has several opportunities like this. It would permit a big variety of distances with economical measuring if this were valid.
Thanks for all the help and education.
Tom