In response to a few questions about increased difficulty of installing the wire insert on 3 layers of 7.2 mil plastic. I have done my experiment with zero added degree of difficulty.
I don’t want to leave it just like that. I would like to add a few points.
First of all, the temperature was about 18C when I did this. It will progressively get more difficult because the plastic is less pliable as the temperature gets colder.
I should follow this up with the same experiment when the temperature is below freezing.
For my experiment I put extra screws into the channel simply to increase the chances of interference between wire insert and screws.
I had one instance where it was a little more tricky and had to push a little harder.
I could see that there could be a possibility where you might need to take out the wire insert and start 1 centimeter over.
There are a few things which I wish to point out on logistics and technique. There is a critical thing to remember for the helper who is pulling on the loose plastic.
He/she must be pulling at least 30 cm ahead of where the wire is going into the channel to allow the necessary slack to get the wire into the channel.
The same applies for the person inside the structure who is pulling on the end wall cover.
Inserting the wire insert is very much a wrist action and proper technique is probably even more important when doing 3 layers of 7.2 mil
Your thumb should be on the next equal bump (either up or down) so that you can apply some twisting action to the insert.
Never simply slide the insert up and down as this can abraid the cover.
I hope this helps