dear CELINE,,,,,,i would still "run" with 1,5 / 2xml per 4xlitres ,,,,,,rennet is very very forgiving and cheap
the only side effect i am aware of is , if you heavily O.D. it will impart quite a noticable bitterness
so be brave , and no doubt you know to apply the diluted rennet widely across the milk then stir it from bottom to top
arrivederci e buon lavora,,,,,,,,,,brian