For a free standing sign structure, look at calculating a base shear with Rw
= 5, then don't "push" the design values on the connections to the maximum
For design and connection...
Try integral tied columns with the wall spanning horizontally for out of
plane. Then develop the column base connection as a rigid connection. This
could be accomplished using embed plates with welded A706 rebar at the panel
and at the foundation with welded steel tie plates between. Allowing for
panel pockets and clear cover, you should be able to develop a full 16"
effective cantilevered column.
A little rough, but an idea....
Paul Feather PE
San Diego, CA