Bench location

[kycat1]

Never had this happen before and need to get others opinion and possible clarification.
High School Sub State match and the benches are set way back (18 to 20 feet from the sideline) since there is no other match on the other court. I know this gives the players more room to chase errant passes and think both coaches would like the extra room. The visiting coach does not like how far back the benches are and after the 1st set asks to move her chair closer to the court. (We cannot move all the chairs as they are on a rug to protect the basketball court). I think of no other rule than that the bench can be no closer to the court than 6 feet. I put a piece of tape down at the 6 foot mark and instruct her to keep the chair back past this point. I also inform her that her bench is now parallel to the side of the court and the front of her chair, not where the other chairs sitting on the rug. This took her playable area from about 20' to about 10'.
Is there anything in the HS rule book the states that the bench must stay where it is placed at the start of the match if the coach wants to move closer and reduce her playable space? Please state rule reference.
Is this something that the Federation needs to include in next years rulings?