Got a horizontal 10″ deep i-beam forming a porch edge. 2x PT top and bottom plate bolted to it. For a 3-coat stucco, do I need sheathing to span the gap between the flanges, or will the lathe be solid enough between there to get a good scratch coat? If we use a 12″ or bigger trowel and run lengthwise rather than bottom to top it wouldn’t sag in the middle, yes? no? And, would ribbed lathe work better than non-ribbed?

Thanks.