Brooweena is not a large Twinshock-only event. There were 30-something riders this year and it has been around that size for many years. Brooweena is located about midway between Central Queensland and Brisbane. Riders mainly come from the coastal strip between Rockhampton and the QLD/NSW border.
The biggest Aussie Twinshock-only trials events are run by the Denman MC in the Hunter Valley, NSW
Note these events are Twinshock/Classic-only. Most other trials are run with Modern and Classic classes.