Fed DOT laws state that you can have a load extending no more than 4' from the taillights. where I work we commonly carry loads on a trailer with more than 20' overhang, we have a lightbar straped to the load no more than 4' from the end... flags can not replace the lightbar, I was riding in a truck thats trailer was rearended with just a flag and the 1st thing the officer asked was where is your lightbar.
Chris
Chris