First, I’d suggest at least two top level relays. If one has a hiccup for any reason, your second tier relays would bog down your root server in your current configuration.
Then I’d recommend creating a relay affiliation strategy for your top and 2nd tier relays. Finally, implement an affiliation seek strategy for your clients to leverage the relay affiliation groups that you’re advertising.
For a simple example, on the top relay side set:
setting "_BESRelay_Register_Affiliation_AdvertisementList"="[Top Relay group name];*" on "{now}" for client
setting "_BESRelay_Selection_AutoSelectableRelay"="1" on "{now}" for client
2nd tier relay set:
setting "_BESRelay_Register_Affiliation_AdvertisementList"="[2nd Relay group name (hint: use relevance substitution to make this variable by location business group etc)];*" on "{now}" for client
setting "_BESRelay_Selection_AutoSelectableRelay"="1" on "{now}" for client
For Clients set:
setting "_BESClient_Register_Affiliation_SeekList"="[2nd Relay group name (hint: use relevance substitution to make this variable by location business group etc)];[Top Relay group name];[optional failover relay name];*" on "{now}" for client
setting "__RelaySelect_Automatic"="1" on "{now}" for client
To make it more sophisticated, create a policy action that sets client affiliation seek groups by subnet. In this way, a laptop, for example, can use the local relay regardless which company location it happens to be at.
Then if you occasionally see clients drift to relays to which they are not normally affiliated, that is the clue that there was some communication and/or relay issue which prevented the preferred relay from servicing their request. When the communication or relay issue is resolved, simple run ‘relay select’ to push the clients back to their properly affiliated relay or simply wait for the clients to do this naturally over time.