Why don't you try it out "without" first? If you hate it put it back on. Even if you trim it to a nub it's worthless. I run my "Deck" without and it's a little tight getting in and out of Gooseflats with another boat passing. And speed wise i doubt you'll notice. It's not too bad you just have to get used to it.
Yes, 5. I had the large rudder on mine, and I took that stupid thing off. At idle, it performed the same with or without. What I really noticed, is that when you're on plane, and you try to turn with the rudder on, it slowed the boat with all the drag it was putting into the water. The rudder was basically acting like a speed brake on an F15 when you tried to turn, it just scrubbed speed. It took a lot of wheel effort to maintain a gradual turn. When I took it off, the steering effort was greatly reduced, it actually turned better allowing the thrust to turn the boat instead of a worthless rudder, the drag was reduced and the speed increased. I'll never put it back on.
Thanks Wet-My boat is also hard to turn the stearing wheel.
I also notice that when I am doing a high speed run that i must keep the wheel perfectly straight. It I turn the wheel a tad, it slows the boat down (like 7-8 mph) even though the direction of the boat does not seam to change. Turn the wheel more then of coarse the boat changes direction.
Does seam to act like a speed brake as you describe