I didn't set up our servo guns, which are Denyo guns, so I don't know if this will help. The material we weld is 1 to 3mm total thickness and our typical clamp force for spot welding is 1 to 3 kn. On our guns, 5kn is enough to force the cap tips all the way against the electrode body. Don't ask how I know this!
We use a TUFFALOY digital force gauge and an ENTRON weld force tester to verify our weld gun settings.