MC-4 connectors are quick and easy but I wouldn't use them on an RV roof. They don't seal well enough. Use marine grade shrink tubes (the kind with melt glue inside). Heat them until the glue flows out of the ends. West Marine is a good source. I guess maybe you could put a real large one over the outside of an MC-4 but it's easier to use crimp-on butt connectors. Use a shrink tube over each wire connection and then a larger one over the whole cable joint. If you do it this way, be sure to keep track of your polarity. -Mark.