Stacked Cheerleaders

[Freddy]

At an area gym, the cheerleaders usually line up in single file with backs to the wall off the endline. Due to the roomy nature of the area off the endline, there has never really been a problem with them getting in the way when we needed to work deep. But they did something different last night which we needed to address. They took up half the lateral area but chose to stack themselves two and sometimes three deep, which brought them closer to the endline and in our way from time-to-time.
The cheerleading coach was advised of our desire for them to revert to a single-deep lineup and outside the free throw lanes extended. She complied but asked her AD what rule existed that she didn't know about. He asked me, and so I'm asking you.
I can't find anything in the NFHS books nor from our state association about cheerleaders on the endline.
Do you know of some documentation that prohibits or addresses this?