I have a closely related question.
I fly sparge, and when I drain my lauter tun into my boil pot, the liquid drops about 8" from the end of my drain tube into the boil pot. Until I've drained a gallon or so, the sweet liqour splashes on the bottom of the pot, creating lots of bubbles and foam. Is this splashing a concern, or is HSA only a problem post-boil?