My Western Mountaineering Ultralite also has open baffles, and the down does migrate. Some people (evidently the kind who stay in one place all night) like this feature so they can shove most of the down to the upper side. I change positions, usually from one side to the other, every hour or so at night, so I really need the down even on all sides. I've found that I need to redistribute the down almost daily during trips. I'm therefore sending my bag off for an overfill this winter. The additional 2 ounces will be worth it, IMHO, and keep me warmer to boot. BTW, the current price for overfill for the Ultralite is more like $20.00 plus shipping both ways for 2 ounces.