Seats in vehicles and level of submergence

Hi all. I got two troubles.
First I d like to ask you how to make a driver also a gunner. What I mean is to make PR-like vehicles to be able to operate with one crew member, so the driver could operate a turret. If it is possible you could upload examples. (I dont have PR on my hardrive at the moment, and I am not trying to make PR vehicles but from ohter mod which has both driver and gunner-it is a boat)

And the second question is hypothetical: Do I have to change something in mesh of this boat to make it a little bit more underwater?(now the engine is sticking out of water and it looks weird). Or can I change something in tweak file, becouse it would be easier?

Appreciate any help.