The old two-sets-of-marks method worked just fine for those who did the actual course layout. It was the certifiers who got confused.
Early on, during the transition period from two to one set of marks, I would get applications lacking the separation of the two marks. This was not always at the end of the measurement. Data for the individual splits was also submitted that way. This got confusing sometimes, because the separation would sometimes seesaw – that is, the two marks for a given split might be separated in a different direction from split to split.
The problem came about because people did not read the instructions. They used the forms, designed for one set of marks, and submitted data for two sets. It was like pulling teeth to get complete information, because they did not write it down and had forgotten.
Although the instructions say to use a steel tape for a final adjustment, this is widely ignored. I know of nobody who always does it. The instructions should be changed. The method Neville proposes for laying out a finish line is just fine – so long as the data is submitted in an understandable manner.
An application for certification is like a surveyor’s report – it must be understandable to the reader. It is not enough for the measurer to know what he is doing – he must convey his methodology in a clear manner to the reader.
The present forms work well for one set of marks. I know of no forms that outline how data should be presented for two sets of marks.