*******, you are correct that an aluminum part requires extra processing to plate. Treated with special cleaners, then a zincate, to fool the bath that it is pot metal, then nickel, and chrome. Steel, much easier. Would like to suggest you add some bosses, for threaded holes.
1) to drill and tap for final installation. 2) to allow some screws to be threaded in. There will be burn marks on this bezel, from plating. I can see this easily pulling 50-100 amps of current, in the chrome tank. By adding bosses for screws, the screws take the high current burn, and are disposable! It would also help the poor guy that has to try to hang onto this part, buffing in preparation for plating. Gotta have a death wish to try and hang onto a thin cross section bezel like this, using an open buffing wheel. Screw holes will allow it to be mounted to a board backing for polishing. If you make it as drawn, better make two. The first one will get pretzelled while buffing. irontoys