The requirement of 3x applies to new construction. However, you can utilize an
existing 2x for wall anchorage. The loads should be concentric on the (E)
framing and adequate nailing to the plywood panel is necessary to develop the
O/P wall loads into the subdiaphragm sheathing. The purpose of using 3x is to
achieve proper nailing pattern at the plywood panels edges without splitting the
framing member and maintaining enough effective area of the framing member after
loss of section due to drilling. An alternative to drilling the (E) 2x is to use
self drilling screws.