nightpiper, surely you must know that exposure compensation is directly related to how you meter. +1EV may work for you simply because of your metering style, but it certainly won't work for someone else who meters differently. You can't claim that it is an ISO25 film marked as 50 unless you can prove that under a specific ambient condition with accurate metering, it fails to render a correct midtone exposure as shot.
Velvia 50 is a very high contrast film with rich and deep blacks, it doesn't have much shadow detail to speak of by nature.