From what it seems people seem to be afraid to do this, because no one else has ever done this, either cause of possible heat problems or because the rear bass port and of course, I'm one of them.
I've contacted dynaudio and they too, did not suggest for me to flush mount them for the same reasons.
Well on this Dynaudio Website... there's a studio with Flush mounted BM6a's ???
Sroll down.
http://www.dynaudioacoustics.dk/Default ... AjrNwsPg=7
So a Professional studio designer flush mounted the dynaudio BM6a...
This gives me hope to flush mount my own.

The studio is called "The Grip":
http://thegripstudio.com/index.htm?id=7731
I really love my BM6a's and I was in a really big dilemma on what I was going to do, If I was going to buy new passive monitors,and that I was going to pay a load of money, again...
Well if a professional studio designer and a professional recording studio trusts these speakers to be flush mounted,then this gives me more reason to flush mount my own Dynaudio BM6a monitors.
Cheers.

Vakis