I am looking for some type of electronics to run a trolley back and forth (point to point operation) on my mantle for the holidays. What I do not want is the trolley banging against the bumper to flip the reversing unit. Is there a product made that will slow the trolley down, stops and reverse, then slowly throttle back up? I'm looking for smooth operation. Or, can anybody point me to a DIY project for this??? thanks!!!