I don't have a Vinci (don't like the way they look), but in my Cordoba, the best combo I have found is either an IC or LM Carlson Extended choke with a Kent 2 3/4" 1.25 oz #3 steel shell. It is absolutely devistating on decoying ducks. I only got out 4 times this last season, but got my limit twice with this combo.
Benelli - Cordoba (20 ga. & 12 ga.)
Browning - 725 Sporting (12 ga.), Maxus (Hunter & MAX-4 Stalker)
Franchi - Renaissance (20 ga.) <-- For Sale. PM me.