Good luck with size 13's on a normal width board... I understand why you bought the board because it's not a bad deal but unless you run extreme angles, a super wide stance or risers which blow it's going to be difficult not to catch your heel or toe in the snow. I'd say do your best to find some footprint reducing boots like the above mentioned Salomon F-series, Burton SLX, Sabbath and a couple of others, Ride also makes or used to make some, Deeluxe also I believe makes some.
Those boots should bring you down to maybe an 11.5 or 12 in actual footprint and then if you're running a wider stance and some aggressive angles you could be fine. The problem with risers from a guy who's been riding since they were pretty much the only option for big footed riders besides the K2 Fatbob and Ride Mountain Series is that they remove a significant amount of board feel. Now if you're just looking to cruise on this board than they'll be ok and not the end of the world but definitely not the best.