As you may know, Talkgroups below 90 are reserved and do not route between BrandMeister master servers. Traffic stays within repeaters on the master. As of version 20171029-191416, the talkgroups below 90 should not be configured as static for any repeater.
For cluster usage, BrandMeister recommends to use Talkgroup 2 and Talkgroup 8.
Reflectors use TalkGroup 9 on Timeslot 2.