Surprised you didn't go with copper, but nice job so far nonetheless!
I have copper pieces to the right of this project.... I'm not sure how they would hold up though as they aren't an alloy. But it may happen in the future.
Make sure your holes line up, and make absolutely sure they are vertical. Check by using the other scale. Clamp the hell out of everything before you drill. I had a drill press with bad spindle bearings, which made the drill wobble as it ran. Drill bits walked, and ran sideways. It was bad.