Suggest you move to the latest stable 6.X firmware as 6.47 is getting a bit stale.
Take a look at this excellent reference. Post number two describes a switch file.
http://forum.mikrotik.com/t/using-routeros-to-vlan-your-network/126489/1
Rules of thumb,
All smart devices should be given IPs on trusted vlan subnet.
For the MT device, the trusted vlan is part of the trunk traffic, even if just to carry that to the next smart device.
Seems easy peasy, one bridge
identify all the vlans passing through with interface bridge
two trunk ports in use
not much else…