I am interconnecting some strip lights in a closet. They are linkable LED fixtures which each come with a connector cable to link, optionally, to additional fixtures. The connector cables are a bit short for what I have in mind, but I need to use their ends because they have special connectors to link the fixtures and maintain correct polarity.
The connector cables are 18-2 SPT-2 lamp cord. I have a spool of the same type of cable. I am planning to cut the connector cable in the middle and insert an appropriate extension length from my spool. My plan is to splice them using some 22-18 butt splices, then heat shrink them with 3/4" tubing. I will ensure the splices are solid and the polarity is correct. Beyond this, what should I do to make sure this setup is safe?
None of this will be behind a wall. The strips will be against the wall, on their mounting brackets, and the cabling can be secured however. If nothing else, I'll just be using cable staples. I could also run all or some of the cabling through conduits, bracketed against the wall. Or I could simple put the spliced areas within junction boxes. Any suggestions for the safest way to do this are welcome.
I realize there may not be a code-approved way of doing this. The cables will not be in a place where they can be routinely touched, and if I were to move out of the house, I would take all of this stuff down, except for the first of the linkable fixtures which was installed with a junction box by an electrician (it is controlled by a light switch).
If you believe there is no way this can be done without a moderate risk of fire, it would be very helpful to hear why you think so.
Update: This particular line of products now has longer lengths of linking cords available. As a result, no splicing needs to be attempted.
EDIT: This is obviously NOT a duplicate question as erroneously suggested as "What size heat shrink tube is required?" and "How can I safely do something?" are completely different questions.