r33h i'll usually only sand the top 1/3 of my calls also but heres a good factor how ever you sand your call the striker you use will create different sounds i'll use a walnut striker then turn to a carbon striker for a more louder effect so keep that in mind i carry about 6 strikers with me if one dont work i'll jump to a different one and see what happens also i found that a 1 piece striker will be more crisp then a 2 piece production striker which comes with most calls

MrGobbler