Pope, I love my louvers and when I was in Miami noticed they really helped keep interior temperatures down in my black pony during those long 95 degree afternoons.
I recommend you try this too: after you clean the window, put on the new 3M tape, and let the tape set for at least 12 hours, take some electrical tape and cut it into pieces about 4 or 5 inches long. You will need 4 pieces for each mounting bracket. Use these pieces to make a square on the window around each bracket, but leave about 1/8th of an inch around each bracket because what you are doing is making a dam around each bracket. Now take somI e clear silicone and make a generous bead in that 1/8th of an inch space. Take your finger and run the silicone bead over and around the bracket and onto the window and this will make you a nice watertight seal around each bracket so your resistance to moisture will be much greater. Let the silicone become semi-dry (no more than half an hour) and then take up the electrical tape slowly so it doesn't take up the silicone with it. Let the silicone dry completely and then mount your louver and you are set! Small bead of silicone won't be visible to you or anyone but it will serve its purpose to protect your double stick tape from moisture.
This worked well for me and I have had my louver on for a year with no problems so far. Good luck!..... Ken