Yeah most tracks are either 1/8 or 1/10 size and spec.
2s for 1/10 and 4s for 1/8 classes. Always been that way. A hard rule for the most part at any serious track. Even if there for open practice running. The Rules apply.
6s anything is absolutley dangerous, a liability on most organized track venues.

Not even track driveable on 3s for 1/10 or 6s on 1/8 rigs.
Running 6s packs is a Basher thing, running out in the wild.