Best source for prefinished teak for a privacy screen wall? Mostly worried about the slats staying straight

Architect spec'd teak slats for a privacy screen off the pool deck, oiled finish. What I keep getting hung up on is the slats twisting or bowing, since they're exposed on all sides with nothing behind them to hide movement. Who's actually supplying prefinished teak for this kind of thing, and is teak really the move or am I overpaying versus ipe?