I made sure to seal the gasket with 3M Black Super Weatherstrip i think its 08008, Green tube at Walmart for ~$5. Theres a DIY for it somewhere on the forums... Actually the comments group buy for the taillights has the DIY on one of the pages....
Edit see post:
http://www.ft86club.com/forums/showp...&postcount=291
http://www.ft86club.com/forums/showp...&postcount=281