I went to site and programmed there for the day.
The last time I tested out two new floorboard runs for the different joist spacing I found a problem near the rear wall.
The only way to investigate this fully was to remove the sheeting above these runs.
Because it was raining I first needed to deploy the large tarpaulin over the work area.
Then the next break in my work - I lifted the sheeting.
These new floorboards are not yet fixed down - just placed in position.
Looking directly from overhead I could see that all the screw positions were correct apart from the very last set - and even these would work.
I took the offending run home and found that my cutting was about 5 mm out - which means all my measurements are still correct.
Saturday - Sunday
Knowing that my marking stick is correct - I went in to mass production of floor board runs.