You can try and call Tower Hobbies/Carl Goldberg for the throws if your surfaces are proportional to the CG Extra.
<u>Don't tell them is a scratch built!</u> Without knowing the surface areas, it would be imposible to predict what degree of deflection is needed. Assumming that all variables and ratios have been kept, generally a dual rate can be set up with 15-20 degrees of throw on elevator and 10-15 on ailerons as the low rate with all you can get for high rate( 60 Dgrs). Use ~20-25% exponential. I would set the high rate just a little above low initially(25-35) just in case the low is not enough and then increase to 3D as you become more comfortable with the aircraft.