Sundhar,
The twelve degrees deflection is how far the control surface will move to each end. In this case, not much movement needed to control the airplane.
The Expo is the amount "softness" you are adding to the control. The center of the stick produces less movement while full stick movement produces full control surface movements. The control surfaces move at an exponential rate to the sticks not a direct or linear rate.
The first can be set up mechanically on your plane by using different hole combinations on the Servo Arm and the Control Horn. Closer to the center of the servo arm and further away on the control horn produces smaller movements. Furthest hole on the servo arm to closest hole on the control surface produces more extreme deflection or "throws". Mechanical advantages also change with these combinations. That means stress on servo gears and higher servo amp draw for extreme throws and less stress with lower draw for less throw. This deflection can also be controlled as a setting in the radio. The radio I linked is capable of this type of programming.
The second, the expo, is just a radio programming option. Again, supported in the radio I linked.
Also, here is a link I thought you might get some use from.
http://flitetest.com/articles/waterproofing-your-airplane
The article is about waterproofing your plane. But, given that you might find it hard to get foam board and your laminating technique might prove heavy, you could cut, sand and shape the foam you have available and give it this covering to make it stronger. Just an idea and I am not sure it will work. If you try it, let us know how it works.
