Yes you need two MB one connect to BM and one for YSF Gateway. Almost similar to the first one you create use YSF Gateway and select FCS.
BM-TG??<->MB_BM<->MB_YSF<->YSF Gateway<->FCS003

Did you download from DVSwitch System Builder a complete package:
https://github.com/DVSwitch/DVSwitch-System-Builder

Looks like Steve have developed a new update to steer TGs in MB, will see how does it work, thank you Steve for this update. :)
73, Eric