I would be concerned with it sinkng from the weight of the copper unless you have it suspended or something. How deep is your grain bed usually?
IMO, the whole sparge arm is a complete waste of time at this scale really. I just run a hose into a little cup that sits in the center of my grain bed. The cup overflows sending water to the sides instead of straight down (which would create a channel). Then just keep about 2-3" water on top of the bed during the sparge. Works great every time!
But, no, I don't think you are going to have a problem with your method as long as the copper doesn't sink down and you have a sufficient grain bed depth.