I think I found how to post a photo. Here is the one I mentioned previously showing B&O's duplex drive 4-4-4-4 on a car-float in 1938.
Note in this case, the middle track is empty and the loads are on each side of the float. This helps reduce the possility of the float 'rolling' (rocking side to side) when encountering wakes of other vessels.
It doubled the weight of the Emerson as ballast, to make the float more stable than if the locomotive alone was on the center track.
S. Islander
