I also fly a Titan (on a Naze32). I'd suggest carefully checking the COG. Make sure it's balanced (adjust battery position).
That said, it seems likely something else is going on here. You stated that Forward trim didn't help with Rightward drift.
This may sound dumb, but did you try to adjust the Left/Right (aileron) trim?
I can usually get it dialed in pretty close. My son, who is a (much) more experienced multirotor pilot, always told me to not worry about minor trim. He said you constantly need to make adjustments when you are flying. If you want a hands-off experience try a DJI.....
When I first started flying LOS, I did a lot of hovering. As I started to fly FPV, I learned that it's much easier to keep flying forward. I don't worry about a perfect trim any more. I heard the Flitetest guys talk about this too. Some of them (Josh B?) fly comfortably on horribly trimmed models. It depends on how you fly - hands-on the sticks or more hands-off.
If you are still struggling try to contact the Vector guys for some help on these forums -
http://www.rcgroups.com/eagle-tree-systems-443/
http://fpvlab.com/forums/forumdisplay.php?40-Eagle-Tree-Systems
Best regards,
PCH