The existing setup already have gateway 192.168.1.254 in both WA5120g. Also I do not use any security encryption for testing purpose. Went through the tutorial to confirm that was what I did in the setup. Just could not believe very poor throughput for only 33 meters outdoor, good signal 55db and power at 21dbM. Am I missing something or AP bridge has much higher overhead compare to AP-Client mode. Have not tried AP-Client mode yet as the setup is at another site.

Just to share what I learned about 2 x TL-WA5120g connected in bridge mode.
1. Was too pre-occupied with using channels 1, 6, 11 which are usually popular and congested in the airwaves. Once I surveyed the least busy channel (which is channel 13 in the environment) throughput shot from 300kbps to average about 10Mbps. This is sufficient considering my source ISP is only 10Mbps.
2. Was also too focus on distance setting. It did not matter if you choose indoor or manual 0.1km. The actual distance is 33meters.
3. Did not matter if I use bridge mode (No AP) or AP-Client mode. It gives you the same throughput. So I stick to bridge mode (No AP).
4. In theory, no encryption should give best throughput because AP cpu does not need to process encryption.

Hope this is able to help someone.