Question about frame perimeter and wheels

[Samwise_T]

We used wood for the prototype and made it a 30x30 square to show to ourselves the max area we can have. On our prototype, the wheels were a few inches outside of the actual frame. However, we noticed per Rule R4 that nothing can extend outside the frame perimeter at the start of the match.

I saw on another post that the wheels would constitute the edge of the frame perimeter. Is this the case?