Also if you have a FCS you can do the same way by replacing DMRGateway to YSFGateway.
Bridging XLX I only use one instance of MB but I point to YSF reflector looks like this:
XLX<->BM<->YSF this is very efficient
To bridge BM -TG I also use one instance of MB and also point to YSF reflector.
This is not a chain both instances run independently in one box. The downside is if you dont have YSF reflector then you go back to square one : (