Towing mirrors

I have a 2012 tundra and use the cipa mirros but with a few mods. Bought them through etrailer and the shipping document said Toyota tundra but they did not fit very well. They have a plastic insert (sleeve) that fits inside the mirror with an abbreviated hole that the outside plastic nut screws in to for tighning the cipa on to your mirror. Well the passenger side loosen and blew off on a country road. It landed in a ditch and did not break. The insert did and etrailer sent me a new one at no cost. I decided to modify it and 6 months later with 3,000 miles neither mirror moved one bit. I bought two bungie cords per mirror at HD and I believe they are 18 " long but they could be 24", they are the thick black rubber ones. They are in storage with my trailer so I can not measure them now. I took off one of the metal "S" hooks and put the remainding hook back into the hole of the cord. I slip that over the cipa and worked in back towards the plastic knob and it is really tight. I then take the other bungie and rap it around the tundra mirror next to the door and hook one S to the back and one to the front of the bungies that is around the mirror. I also put plastic tubing around the S hooks to prevent damaging my toyo mirrors. Again they will not move and cannot blow off. Good luck. Tuna