I have two set up. One I can move and use on the power line up to any distance and oneI shoot across my BILs lake (310yds). I use 1/2"steel plate I picked up at the truck repair shop nearby (they do a lot of welding). I hangboth from rope and let the bottom swing but it is restricted by a bar across the bottom so it doesn't spin around if hit on the edge. This allows it to settle back quickly.

You can really hear it ring!! Especially with MLs.