So that was something of a red herring then....
You'd be better off calculating the downwash speed for a selection of helicopters - then apply the notion that your RoD has to be at least 0.6 and ideally 0.75 of your downwash speed to encounter actual VRS (according to wind tunnel tests and modelling).
Then see if the Vuichard technique works at those rates of descent with 50' to 100' recovery.