Always AHEAD of the axle, as far ahead as you can get it, the one on my 1 ton is approx 12 inches ahead.
Directly over is a common mistake, that leads to a teeter-totter effect that you WILL feel.
1969 massey 135 and a 2013 m7040hd 4x4 2013 L3800 HST 4x4
Put the gn plate on the rails on the bed its self before the axle like its suppose to be . No really hard to do . Most flat beds have the plate build in the bed its self and not on the frame . With the bed lowered down it will pull fine .
Check out these cannonball beds . I know there hay beds but there dumps also a all around bed .