What's the best shape and material for my Wi-Fi range booster dish?
It's cheapiness make it worth the shot. Hours of fun for little money.

Also the cantennas seem to work well:

http://www.turnpoint.net/wireless/cantennahowto.html

Maybe, the stick signal is too weak. There's also the problem of carry the USB signal from the roof to the apartment. The maximum cable length for USB 2.0 it's about 5 meters according the standard.