Some time ago I read on mikrotik manuall that there is no way to bridge the nstreme dual connection.
I found test results of rb112:
http://www.mikrotik.com/download/rb112test.pdf
There is a results
"Nstreme DUAL between RB112 conn-track enabled, bridging !!"
I have never tried to bridge the dual nstreme.
Is it possible ?
Simple nstreme works great in bridge with wds.
Regards
Marcin