Yeah, all that contact with the firehoses is going to cause dampening of the vibrations of the steel. Remember that sound is just vibration. You want the steel to vibrate as freely as possible. Area of contact with other objects should be minimized.
Go look at how cymbals are mounted on a drumset for an example of how to get a metal plate vibrating very freely. You can't copy that, but the closer you can get to it the better.
Go look at how cymbals are mounted on a drumset for an example of how to get a metal plate vibrating very freely. You can't copy that, but the closer you can get to it the better.