It’s difficult to say how long a cart will take, because it depends on the contents of the boxes. Between the TL and ETL’s standards, I’d follow the ETL‘s direction if possible. The ETL can cause you a lot more trouble than the TL can, and the TL won’t be upset that you are completing tasks faster than expected. I don’t know what the Greenfield times are, but if you follow your ETL’s direction you should be ok. Hopefully, anyway. Good luck.