XRAY - Model racing cars

Is there a good way to tell how much life is left on the clutch bell.
I don't dremel it to flatten the grooves from the shoes so it's a bit difficult to measure the thickness of the metal left.
Xray shoes seem to eat up the bell a bit too much compared to other shoes although they(Xray) do last way longer.

i clean the bell with a dremel ..if i dont then the shoes tend not to last as long ...bell prolly changed about every 3 sets of shoes or before

i have them 20 litres and it seem's to last at least 10~15 litres more

M2C racings, shoes have the spring on the side of the shoe as well

What kind of pads are you guys using on the dermal to clean the bell??