I heard some rattle when going over bumps. I found that the electronic speed control is not mounted in the tank. It is loose, no fasteners.  Is this normal / correct?
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Hi, do you mean the controller unit in tank? It's a silver metal box.
Yes it's not mounted in the tank. Since the space there is quite limited, it should be placed really tight. 
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I had the same problem. I used some of the packaging foam wrap and wrapped the controller to prevent rattling. It worked.
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