OOOOOH...you have to becareful with your back windsheild!!!!
you do not want to ruin your defogger!!!
i went to a professional to ask a few questions and he told me that he can't be sure if the defogger lines will work after he takes off the tint.
check with a professional.
i personally have never remove tint...so i'm not sure.
i have only applied tint to my windows
best of luck to you