ground the head off of one of the rivits for the rear spring hanger and with a regulat size hammer and piece of rod the rivit does not want to move. How hard is it usually to knock a rivit out of the frame once you grind the head off? should a small sledge hammer and a punch knock one out or do i need more than this? Read where others said it was a pain but did not see anyone say exactly how hard it was to drive one out of the frame. Should i use something else for this like?