The rule as written says the lateral supports must come forward to the furtherest point of the helmet.. so with the helmet up against the head rest,,, the side supports must come as far forward as the front most part of the helmet,,, which would be the chin bar of the helmet,,
so if the helmet is 14 inches long, the the side bars would be ok at 14.01 inch long. it does not say they side supports must be xxx longer.
Just my read on it !!!!
Charles