Is that the final materials for your base?
Yeah, it will be (probably with a few weight saving holes). The rear and the sides will be also be PVC covered.

Also curious what the second mixer you referees to is for?
I must confess, I've no experience with secondary mixers beyond what I've read here, The Honey Badger uses a proper tank RC controller so doesn't need a mixer and Osu uses a Sabretooth dual 5A so again, doesn't need one. I was considering something simple like this.