Bruce is correct about the weak point of a stick framed 2x4 wall. This can be mitigated by sheatheing the wall with 1/2" plywood where the top of the sheeting is fastened into the top plate as well as to the studs. A sheathed wall, along with the fact that you are only extending out 12", and you should have no problems. I'm not an engineer, but did stay at a Holiday Inn last night!