Chasers right on the money. I have boated a lot a fish with out a black box, but you gotta know the depth and where the bait balls are. Go with the FF! You may also want to take a voltage reading reading on your downrigger cables. If you are already running between .6 and .7 vdc, you are in the Zone as it is and a Black box really isn't going to do anything for you.
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M Go Blue!