How do I make a circular track that skate wheels will engage on?

I have a 4’ outer diameter 3/4" thick plywood ring ID is 37"
Underneath it has 6 skateboard wheels of which 2 are powered by 435rpm motors opposite one another.
it rides on a g rooved ring in plywood.
since the plywood ring and track are not perfectly flat the wheels do not always touch.
would increasing the number of motors to 3 or 4 help out much?
any easy way to keep the plywood flatter without spending a forutune?
Rotating ring - YouTube
above video shows the project so far.

Hello @metalmaslow ,

Welcome to RobotShop support.

You can increase the number of the motors and keep them at equal distances from each other.

You can also try to add weight to the ring to make the free skateboard wheels have better contact with the grove.

Let us know if you need further assistance.

Sincerely,