Its been awhile since I messed with the upfitters but If I remember right #3 has a 15 amp fuse which is the one I have my 40 connected to without any problems. Rigid had included a 15 amp fuse in the harness that came with the 40 but after reading that 5 amps per 10 inch of LED was recommended I called Rigid on it, they said some people were complaining of flickering so now recommend changing the 15 to a 20 amp even though it won't draw that much anyway.
I had a 4 inch LED light that would blow fuses and the problem turned out to be a single strand of wire hanging over the edge of the circuit board that would touch the aluminum housing of the light and pop the fuse.