Not trying to be obnoxious or anything but I hope you have up to $4000 available if caught and prosecuted. And if they want to make a statement, and the nightly news, being met by feds and escorted off the plane etc. etc.. Not worth it IMO.
What's the Penalty for Using an E-Cigarette on a Plane?
People are very paranoid on seriously packed planes these days. Don't kid yourself, you will very likely be noticed by someone. Eyes are constantly roaming the cabin. Window seat or not and forget the bathrooms.
Worst case you may have someone from FAMS (air marshal) sitting nearby who notices you. Busted.
I used to fly all over the globe in my profession (30+ years). I was always in the air going here or there. Take it from someone who flew all the time - travel pre 9/11 versus post are two totally different beasts.
Good luck