I did not use the plastic 'insulators' I went straight with lots of electrical tape. I did use the connectors on a few other flexwatt pieces I did, but after seeing many others not use them and even on some cases just soldering the wires directly to the heat tape I figured I would see how I liked it. As long as you are sure to cover every exposed wire/conductive parts of the flexwatt it seems to be ok. I still have a bit of 'lift' towards the back of the cages where the heat tape connectors are, but not enough to really notice.. unless you are like me and notice everything 
here is a pic of what I did... like others say when posting pics of their flexwatt setups: I do not recommend doing it this way. Read up on how to properly do it and go from there. Note also that there are 2 wires coming from the tape.. I also wired mine in 'parallel' so that I would only have one plug for each stack of cages.. Best of luck whatever you do! I love these cages! 
