I strongly am against those line taps.... I've seen them fail to many times even if used correctly.
If I'm going to tap into a wire I personally either
A. strip the wire where I want to tap in using a razor blade and then solder a wire to it and then wrap in electrical tape
B. Cut the wire attach connectors and make a splitter like this.
I would rather spend the time to do it right the first time rather than having to go back and fix it later... Depending on my work space depend on which way I do it.
Just my .02
Tow rig - 2006 F350 with some goodies
Trailer - 2014 T27FQDX
Toys - 2005 yfz450 with some goodies, 2005 rhino 660