Terence,
I usually carry a bowie on me for backup to finish them off if necessary. When hog hunting with a bow, especially, things can get up close and personal pretty quick.
Here are a couple that I made that are good for that. Notice the handles have texture or features that help push/pull grip.
8 inch blade
10 inch blade
I imagine an 8 inch blade is plenty, but some would want a little longer one. I carry a 10 just because I most likely will use it more for it's chopping ability in the bushes.
Of course, anytime you carry a big knife and a bow, you have to put some thought into the carry system so it wont interfer with drawing your bow.
Ray Hammond told me about he and Dan Masson (Oconeedan) after a hog and things got pretty hairy. The hog got too close for the bow with him and the hog on the ground. Ray is intent on having a 9 inch bowie on his side soon.