While I don't want to stop you from building your prop as you see fit, I also don't necessarily recommend that you or anyone try to exactly replicate all of these apparent anomalies of the original prop. Just because it was built in a seemingly slapdash fashion, doesn't mean that it was meant to appear so on screen.
On the other hand, since the film was based on what were originally hand-drawn newspaper comic strips, perhaps the makers did intend for the prop to have irregularities that would evoke the feeling of being hand-drawn (whatever that might mean, in regard to a live-action film!)
So it's up to you, whether you want to build an exact screen-accurate replica, or an "idealized" version representing what the production's prop makers would have made if they had unlimited time and budget resources and were striving for perfection, or something in-between.