Hey Winforever,
Ive had 2 snowboards in my V with the back seat down, although i did not have much other luggage in there at the time as i hired the boards down in perisher.
depending on the shape of your bag you may be able to get a couple of smaller bags in the boot there with 2 boards and back seat down, then you could put bags ontop of the folded down back seat.
I think roof racks for snowboards would be a good idea but ive never seen any that fit the V, might be interested in some though at some point.
hope this helps