Conventionally it does. Thrust implies an applied force (whether accelerating or otherwise), drag implies a resistive force. You are right on the up and down tho' - direction is pretty meaningless - it is just a force.
ANYWAY - whatever - thing sticks down, back goes up (of the boat
), nose comes down, speed goes up, everyone's a winner!!
I'd be interested to know what sort of difference you notice on a 9m RIB, it's not something I've considered before because of the hassle, but if the volvo QL ones improve things (esp rough water handling) then it would be worth thinking about.
When do you think you'll be getting the RIB?