This setting --avalon8-voltage-level-offset has no effect on mining speed so I set --avalon8-voltage-level +3 with results and it loos like +5 is the default setting.

around a 1000GHs drop and a slight temperature drop.

13204.45
30/70

13447.80
29/74

13630.70
29/74

GHSav
39591.71