Hi Anthony,
Can't offer much as far as Samoa goes. I've fished there (south side of Upolu) but the group I was with was only after pelagics. There are some good looking areas with serious drop offs but as you know, Samoa is a seamount and doesn't have the vast lagoon and reef systems that GT"s thrive on as seen in New Cal, Fiji. In Samoa, I'd turn my attention to what jigging options you can create, I don't know of anyone doing this over there.
Fiji in Feb, my advice would be to offset costs and join a group, fish 4 days or so. It's peak season for surface fishing that time of year and you'd stand a good shot at the kind of GT's you're after. A few good options around.
Cheers David