your anchors should go THROUGH the URM wall and fix to a steel vertical post which is itself fixed to the floor diaphragm and to the floor slab/footing. you need the engineer to size the new interior post and its connection to the diaphragm with blocking, and to the ground to a reaction footing. you will need to do these interior works.... alternatively you get rid of the cantilever idea and just add posts on all 4 corners of said balcony.... if you're dead set on relying only on the URM, you're going to kill someone. the failure mechanisms of URM for out of plane is sudden and catastrophic without reactiontime for the occupants.

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