I think that first, the model has to be facing front in the z axis and the side in the x or viceversa because if you are going to use a planar proyection on the prongs the result is going to be better if they are facing the x or z axis because the proyection comes in x,z, and y.
So for the prongs of the sides use a planar on z, and for the one in front and back use a planar on x only selecting the polys on the sides
For the top and down of the 4 prongs use a planar proyection in the y axis.
And for the center a cilindrical mapping will do.
And a planar on y for the top and bottom of the center.