Appowner

Your design is going to put a tremendous load on those servos. A couple of points:
1. The best mechanical advantage is achieved using the shortest servo arm and the longest control horn. But in your case, I'd shorten the control horns too and even try to go in a hole or two on the servo arms. As you shorten the control arms you'll see more effective throw from the servos. But you'll also increase the load on the servos. It's a balancing act in the end.

2. Those servos are probably not up to the task at hand. Any idea what their torque rating is? I really think you'll need something much more powerful. I'd also mount them with something more than glue on the bottom. They have mounting tabs, use them.

3. The pivot is all well and good as it is but the top of the assembly needs support too. When the motors are running the whole thing will try to tilt forward. This will attempt to jam the pivot even with ball bearings. That in turn will increase servo load among other things. A simple support (wood stick) from the front part of the hull up to the top of the motor assembly with a simple pivot on top will work. A simple pivot can be a brass tab on the support with a hole in it. Two brass washers, one above and one below the tab. And a long screw through it and sunk into the top of the assembly.

4. The control arms on your motor assembly appear to be brass wire or similar. This is too soft for this use, they will flex and reduce your control. They should be something like a servo arm that sticks maybe an inch or two from each side of the pivot.

5. Last but not least, when using two servos on the same control, you should use the same hole in the servo arm. You have one in the rear most hole and the other in the front most hole. Since you want equal travel in both directions, put them both in the center hole on the end of the arm.

Hope this helps.