have a look at the fuse and holder design . the contact area can be very small especially important for the the larger fuses in the range .for the standard size fuse 30 amp is the largest size . the same problem still exists with the larger maxi fuse holder but would be better with a lower rated fuse in it , not sure if they make a 30 amp fuse for a maxi fuse holder . the midi and mega fuse holders are better although i am not sure if they come with waterproof housings . and i think yendor has a point , if there is a problem with one side , seperate fuses might keep the car driveable .