i never rack with airlock activity still going. that's a noob thing. it decreases the yeast count when yeast is needed still; otherwise, the yeast would be still. if you're looking at 7% or thereabouts, like two-hearted is, i'd probably 3-week primary, 2-week secondary it to let it smooth a little. there's a lot of talk about primary vs secondary, and lots of people will chime in either way, but that's just me. no, a blow-off vs airlock shouldn't cause any problems, either
If we knew what it was we were doing, it would not be called research, would it?