Design choice and max weight+bending for cantilever
Design 1 does not look like a cantilever design. It looks like the ends of the boards are attached to vertical posts. No, I don’t think this design will work. 

In Design 2, the two outside boards look like a cantilever, but the middle board looks like the end of the board is attached to something, but I’m not sure how it’s attached. 

You could use a couple of 2x4’s (on edge) for a 6’ cantilever to support about 220 lbs. (half of total estimated weight) but how the connections are made are critical. 

I’d use the vertical sheathing to stiffen the cantilever, but again, how it’s all connected is critical. 

BTW, I doubt if your total load is just 440 lbs.  (Total load includes “live load” plus “dead load”.) Also, as you suggest, movement will cause the cantilever to bounce and put extra stress on the supports.