I followed this guide when I got new targa seals all around and used a lot of clear RTV silicone and figured out to use a generous amount where the targa and drip rail meet enough to where it would come through the top side of the targa in the drip rail and just wiped off the excess. No leaks since.
http://gallery.sanitylapse.com/v/supra/Targa+Seal+Fix+10-28-05/
http://gallery.sanitylapse.com/v/supra/Targa+Seal+Fix+10-28-05/