need help with nstreme dual

Hello,

i have two RB 800 (v 5.1 / 4x R52Hn) with two 8 dbi dual antenna (indoor / same type) for test purposes!

In my configuration i get 40 Mbit/s but i try to get more!
Please can anybody show me a configuration how I can get more performance!

My config:

Nstreme:

[admin@MikroTik] /interface wireless> nstreme-dual print
Flags: X - disabled, R - running 
 0  R name="nstreme1" mtu=1500 l2mtu=2290 mac-address=00:0C:42:64:41:E3 
      arp=enabled disable-running-check=no tx-radio=wlan2 rx-radio=wlan1 
      remote-mac=00:0C:42:64:41:DE tx-band=(unknown) tx-channel-width=20mhz 
      tx-frequency=5280 rx-band=(unknown) rx-channel-width=20mhz 
      rx-frequency=5180 disable-csma=no rates-b=1Mbps,2Mbps,5.5Mbps,11Mbps 
      rates-a/g=6Mbps,9Mbps,12Mbps,18Mbps,24Mbps,36Mbps,48Mbps,54Mbps 
      ht-rates=1,2,3,4,5,6,7,8 ht-guard-interval=long ht-channel-width=20mhz 
      ht-streams=single framer-policy=best-fit framer-limit=2560

Wlan1/2:

[admin@MikroTik] /interface wireless> print                 
Flags: X - disabled, R - running 
 0    name="wlan1" mtu=1500 mac-address=00:0C:42:64:41:E3 arp=enabled 
      interface-type=Atheros 11N mode=nstreme-dual-slave ssid="MikroTik" 
      frequency=5180 band=5ghz-onlyn channel-width=20mhz scan-list=default 
      wireless-protocol=nstreme wds-mode=disabled wds-default-bridge=none 
      wds-ignore-ssid=no bridge-mode=enabled default-authentication=yes 
      default-forwarding=yes default-ap-tx-limit=0 default-client-tx-limit=0 
      hide-ssid=no security-profile=default compression=no 

 1    name="wlan2" mtu=1500 mac-address=00:0C:42:64:41:E7 arp=enabled 
      interface-type=Atheros 11N mode=nstreme-dual-slave ssid="MikroTik" 
      frequency=5180 band=5ghz-onlyn channel-width=20mhz scan-list=default 
      wireless-protocol=nstreme wds-mode=disabled wds-default-bridge=none 
      wds-ignore-ssid=no bridge-mode=enabled default-authentication=yes 
      default-forwarding=yes default-ap-tx-limit=0 default-client-tx-limit=0 
      hide-ssid=no security-profile=default compression=no

thx,

tom