I am planning on installing a sub-panel in my attached garage so that I can operate a welder and other equipment which runs off of 240V. The sub-panel will be fed from a 100 amp breaker in the main service panel. The main panel is mounted on an exterior wall of the garage (I am in southern California) and the sub-panel will be mounted a short distance away (about 6 feet) on the inside of the same wall. To route the power from the main panel I was planning on running three #3AWG THHN conductors and one #8 AWG bare copper conductor through 1" FMC. The sub-panel will be flush mounted on the inside wall and the FMC will be routed through the wall studs and buried behind the drywall. I am going to use a 1" x 90deg rigid metal conduit swept bend to come out of the bottom of the main-panel and through the opening in the outer wall OSB sheathing (the main-panel is installed in an stucco faced outcropping so that it actually sits outside the plane of the primary OSB sheathing). It is at that point that I would transition into the FMC.
Is this a proper design? Are there any issues with using aluminum FMC instead of steel to connect the main panel to the sub-panel? The AHJ is the city of Los Angeles.