X1,X2,X3 LEAVE ZONE 3 ON 1. WHEN THEY CROSS NEAR BLUE LINE, X7 BACKCHECKS. X7 NEEDS TO FOCUS ON TRAILER. AS SOON AS SHOT IS TAKEN X4,X5,X6 TAKE OFF. D3,D4 NEED TO BE IN POSITION ON BLUE LINE WHEN X4,5,6 TAKE OFF. X8 BACKCHECKS WHEN LINE LEAVES ZONE. AFTER SHOT X1,X2,X3 GO AGAIN WITH X9 BACKCHECKING.