One of the key attributes of the F6 is the circuitry contained to run the Nikon Creative Lighting System, or CLS. While common among digital cameras, no other Nikon film SLR contains this ability. If you're not using your F6 + CLS you're missing out on one of the wonderful features that make the F6 unique.
As it turned out, shooting Ektar at ISO400 - while not something I'd have thought to do intentionally - produced great results. It allowed working with higher shutter speeds to combat a slight breeze shifting the flowers ever so slightly. Pushing Ektar also amplified the natural tendencies of this already vivid, contrasty film.