I don't understand why you need this fuse. If using the lynx power in, then the lynx smart shut hooked to the lynx power distribution box. The power in box connects the batteries then the smart shunt to monitor solar charging from the power distribution box. The power distribution box requires fuses on all the positive connections, both the solar and the positive cable powering the inverter. Isn't the fuse required in the smart shut redundant when you already have fuses at the lynx power distribution box?
800 amp 24v battery bank with 1600 watts of solar powering the MultiPlus-II_24V_3kVA_2x120V inverter.