WLAN/WiFi (802.11b/g) and Bluetooth coexistence

Hi, I am designing a board with both Bluetooth and WiFi and was wondering about the coexistance problem. I am aware of AFH and proprietary methods of TDM and/or FDM such as priority activity signalling and communication between each chips microcontrollers. As my design is at the physical level (not firmware) I was hoping for any tips on spatial seperation (distance, polarization, etc) methods to minimize interference between the two antennas. Board dimensions and layout currently limit the absolute distance between the two ceramic chip antennas to about 50mm. I have also tried to orientate the two antennas orthogonally so that each antennas minimum gain (referring to their datasheet) is directed towards the respective antennas. The ground plane making up the counterpoise for each antenna is currently connected along a long edge. I have used four rows of vias (at 1mm intervals) to try to isolate the RF energy in the two counterpoises. Will this work? Is it necessary? Also, with vias connecting the different layers of the counterpoise what is the recommended spacing/density if any. Any help with this antenna coexistence problem is greatly appreciated.