If you want a fast roll rate ,then 30 degrees (up and down)is probably at least what you want.If the hinge gap is too tight,you may not achieve that.Remove hinges and install new ones if that is the case.
45 ounce servos are weak.With a 91 up front at cruise, a 55 ounce servo would be minimum,Servo arms(1 inch) and solid linkages is another considerarion.Sealing the gaps as mentioned is good practice.
For sealing I have used clear scotch tape on the underside of planes up to 1/4 scale.