It depends on your final purpose. If you plan to scan, esp. from a non-drum scanner that can't handle the DMax, then you'd better meter to keep the slides a wee bit thinner than normal. If you plan to project optically, then you may actually want to do the opposite. Saturated slides look yummy when projected!

In any case, I don't see much point in dueling with velvia 50, when the newer velvias and astia 100F give you more range at normal exposure.