I use 10# Seagaur InvisX for my T-rigs. My setup is similar to yours, 6'6" BPS Extreme MH with a Chromica 100B.
Your reel has a bigger capacity so 12-15# sounds good to me. Like I said I favor seaguar but have had good experience with Sunline too.
If you can afford to pay $40 for Seaguar Tatsu, go for it. The more economical choices are AbrasX, InvisX, Red Label, and FC Sniper.
Sunline FC Sniper
Seaguar Tatsu
Seaguar InvisX