About DEET melting plastic, I did some tests/posted them on ASC a few years back, using old/broken M16 receivers and stuff.
In sum, what i found was you dont want to ever spray DEET directly onto plastic. Once the DEET is applied and has dried off, its pretty safe around plastic, even if you sweat. Considering 100% DEET is good for ~8 hrs+, its not that hard to apply and wait 15 minutes.
__________________
|