For heavily loaded walls, we place 6" channels "toes down" over the flutes and weld them to the supports below. For walls parallel to the deck flutes (perpendicular to the joists), use a continuous channel (or two if you can't locate the wall well with one). For walls perpendicular to the deck, use short channels spanning between the joists spaced every couple of feet and either design the bottom track to span between the channels or place a continuous angle or channel under the bottom track of the wall. We've had good luck with 3" deep bottom tracks in this condition.