I was in the same boat when I thought about the license plate, but after seeing others relocate theirs - I moved mine and bought the 20" Rigid. Two 4" a 20" do not make.
My first design was to install the hidden winch mount and winch, with 4" Rigids on each side. Then there is a license plate mount that clips onto the winch rollers. This is still my ultimate choice and may do this in the future.
OK, so here's my advise: Cut the bracket in half, or even remove the whole section between the two 4" brackets. Mount the 4" brackets with one bolt each. I think if you mount them tight enough they will stay in place.
You could also drill a second hole an inch away from the first hole - then use two bolts for each 4" section. Since the bracket has a long slot for mounting, I think there is room for two bolts side by side.
before:
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