When two duck hunters are seated back-to-back in a boat, the size of their zone-of-fire is determined by the size of the boat and the positioning of the two hunters. In general, each hunter will have a zone-of-fire equal to the amount of area that can be reached by their arms and shotshells. This includes the area in front of them, to their sides, and behind them, depending on how far they can reach with their arms and the range of their shotshells.

The size of the zone-of-fire is important because it affects the number of ducks that can be brought down by both hunters. A smaller zone-of-fire means that the hunters may not be able to take down as many ducks, as they may not have enough time or space to shoot. Therefore, it is important that the two hunters ensure that they have adequate space to reach as many ducks as possible.

If the two hunters are seated in a large boat, they could potentially have a zone-of-fire that covers a much larger area. This could be accomplished by positioning the two hunters further apart, with one hunter facing forward and the other hunter facing backward, or vice versa. This way, the two hunters would have a combined zone-of-fire that is much larger than if they are seated back-to-back in the same boat.

In conclusion, the size of the zone-of-fire for each hunter when seated back-to-back in a boat is largely determined by the size of the boat and the positioning of the two hunters. With a large boat and proper positioning, the two hunters could have a much larger combined zone-of-fire that would enable them to take down more ducks. Ultimately, it is important that the two hunters choose a boat that is big enough for them to comfortably maneuver in, so they can maximize their chances of success.