Gun Recoil Question in Weapon Design Options

[WearzManySkins]

Ok I thinking of designing a weapon with two barrels in a over and under configuration.

Questions for those here

1. If both barrels are fired at the same time what would you consider the most correct recoil mods?(from the information given by Lagomorph firing two barrels of the Elephant gun, it would be +1 DV, -1 recoil, -2 recoil with out shock pad)

2. What would be the recoil mods for both barrels firing bursts?(3 bullets from each barrel, so a total of 6 bullets fired)

3. What would be the recoil mods for both barrels firing long bursts?(6 bullets from each barrel, so a total of 12 bullets fired)

4. What would be the recoil mods for both barrels firing full bursts?(10 bullets from each barrel, so a total of 20 bullets fired)

I have more question relating to the design but would like to get the recoil mods done first.