I've read over page 37 a few times. My understanding is grass must always be steel taped. I also note the recommended procedure, to avoid errors, is using a calibrated bicycle for the entire course. For previous courses with a shorter distance of grass I have handled this in the notes. I note the start and finish counts across the grass then convert the counts to distance. I then tape the grass. There has always been slippage across the grass, making the course a little longer and proving it isn't shorter, but for simplicity I ride the entire course from start to finish.
So if there is no form... Just follow the example on page 53 of the manual?
Desired course length, 21120 feet. Measured course length 19920 feet. Use a steel tape to add 1200 feet.
Because it is steel tape, I don't think it needs to be steel taped twice but gross error check it with the bicycle and explain in the notes.