Rudy,
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:
First instance:
XLX<->BM<->YSF   this is very efficient 

To bridge BM -TG I also use one instance of MB and also point to YSF reflector.
Second instance:
BM-TG<->MB<->YSF 

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 : (
73, Eric