We have the trees setup in double rows 5' apart with a 12' isle in between double rows, that's why there is 2 different marker lengths.  We planted around 5100 trees in three or four days this spring. 

 I once talked to an older gentle man who told a story about how some neighbor boys got into a fist fight over who got to drive the JD A instead of the AC WD 45. It seems either you love em or you don't.