Homburg got his first championship try on 19 November 1966, when he contested Piero del Papa for the EBU Regional Light Heavyweight title in Berlin. Homburg was defeated by an eleventh round disqualification against Del Papa, who later lost by a first round knockout to Vicente Rondon in a challenge for the WBA World Light Heavyweight title. Grupe successfully knocked out Del Papa, but the referee declared Grupe's head movement to be an illegal headbutt in the 11th round and awarded the match for Del Papa.