It is not a good shot - you will Never hit the heart with that shot - you have a 3 or 4 inch window to at the best hit one lung or the liver. A double lunger will almost never happen with that shot. You are almost guaranteed a long tough track nomatter how well you hit the spot you are aiming for. It is best IMO to let them walk - and take your chances.
I have to agree w/ rack on this one. Let him walk by, if he smells you, he smells you, if he doesn' t, then there' s the opportunity for that double lung shot.