http://www.bateau.com/plans/power/XF20_study.htm
Check out this plan it shows a pocket tunnel boat plan, Kenner boats puts these on some of thier v-hulls, because it is at the back of the boat it does not have a huge effect on the ride characteristics (unless you get the enitre hull out of the water). The water will fill the tunnel and the prop can run behind the tunnel area and thus provide more draft.