I know Dan and his wife were early adopters of Ben's pants, so he might have changed the specs since then, but my 1 year old down pants, and my gf's 1 day old down pants both have 5" baffles. I do not notice down migration, nor am I worried. These are part of my sleeping system...I don't hike in them. So when I'm getting horizontal and catching Z's, down migration is non existent. When I walk around camp, I haven't noticed down ending up at the bottom of the baffles.
If you were really worried, I'm sure you could specify baffle height.