I’ve got a AEM air fuel ratio (AFR) gauge and need help deciding where to put the widenband sensor. I’ve read conflicting advice on how far it should be from the turbo but has anyone got any first hand experience please?

Most people seem to say at least 18 inches from the turbo but a lot of cossies seem to have sensors much nearer than that like this one below. I’m torn whether to mount it at the top of the downpipe or further down the exhaust. Any experience please?