Which type do you have and what is it like to use? Our crush rails are made from box section so I think they should still slide down them okay. I've seen the single bar ones and other broader ones with two bars joined at end (rectangular shape).
Single bar seems to allow rotation upwards out of way whereas the twin bar type needs to be pulled out and pushed in behind them - or rotated in from behind. I would have thought that the single bar would be prone to cattle rearing up on top of them - is that an issue?