Wideband location on WRX

I will be tuning my '03 WRX soon and would like some of your imput on wideband location. The Bosch manual says something like 8-12" from the turbo, I dont have a bung there, but I have my rear O2 bung though. I didn’t measure yet, but would assume its ~3 feet from turbo. Looking on some Subaru forums…some people have a bung within 8", some are using the stock rear o2 bung. Some one quoted “Mark” from Turboxs saying that you don’t want the sensor to close to the turbo.
I also read that you will get a slightly leaner reading at ~2-3 feet opposed to if it were 8" away…how much leaner?
If anyone has any experiance please chime in.

edit: so how far away are other people going? on any car.