Wifi APs, like everything that deals with radiowaves, must be placed as high as possible. Free of every obsticles, walls. On such super high frequency it is very important to avoid having metal parts nearby the antenna.
Gain is something that you must take with care. Manufacturers try to put whistle and bells in their product specs, and promise you wonderful gain they can not achieve. You can bend physics as you like.....
The Struggle Continues...
Asus WL500g #1 with fw 1.9.2.7-7f running as main home gateway, with Philipps PWC730k
Asus WL500g #2 with fw 1.9.2.7-7f running as Wireless Client, running palantir 2.6 with SPCA5xx camera on 128MB generic USB key