Hi,
Appologies in Advance if you have allready tried this. I have meshed several IAP 275's and found upgrading the firmware past 6.4.4.8-4.2.4.2_56164 has broken the mesh function. Basically the remote AP goes into a constant reboot, i ended up backdating firmware to make it work. It looks like the minimum firmware is probly 6.5 for a 207 so that will not help you in this case. I have found wireless meshing Aruba products has allways been DIFFICULT no matter what make model or firmware version.
So first thing is to build your cluster as per normal. Set Extended SSID to Disabled > then set Eth0 briding: To Enabled (on your non wired remote ap) once you reboot both Ap's it can take up to 10 minutes to mesh the remote AP.
To make the remote AP (wirelessly meshed access point) bridge to another wired network or switch do the following. Select the More drop down menu then select Wired. Select default_wired_port_profile then press the Edit button. Change the Admin Status menu to Up & Uplink menu to Enabled. Click Next twice then select Finish. Reboot ALL access points from the Maintenance Menu. Now reboot (yes again) your remote access point wait 10 minutes wired bridging should now work.