I've found the trick with the square plastic thingy's with the double faced tape is to stick them, then leave them for a day. Then load them up. Apparently the tape needs time to "set". I've had some in service for years. Unfortunatly you can't do that when you are on a job, and need to get it done and get on with it. I have the luxury of time, on most of my projects.
It also helps to make sure that the wires aren't trying to pull them off, ie bend the wires so that the tywrap just keeps them there, don't use it to pull them there.
TW
