Reducing Velvia's contrast though reduces the effect that Velvia sets out in the first place, using contrast and palette to deliver punch, in lighting matched to the design parameters of the film. The heavy contrast and touchy latitude can be too much for some people, but like everything, you get better with it with lots of experience! Provia 100 is a good, lower contrast alternative but a pastier palette. Experimentally, GNDs with multi-patter/evaluative metering systems can confuse the reading. Run tests specific to your camera before committing a GND to an important shoo.