Cycling UK Forum

Could anybody help me with this, I have a trek sl6 gen 4, and I am trying to fit a garmin cadence sensor, the crank arm is like concave on the inner side so the sensor is not like a solid piece of metal so there is “well” where the sensor would fall into when you try to attach the bands to the sensor around the crank arm. it’s almost like having to use something to pack out the crank to getting it fitted, anybody had this problem TIA