help with O2 sensor

I need to add an O2 sensor to my exhaust for my RCR Razor. I have purchased a Denso wide-band unit and found a steel nut which has the right thread. I intend to weld this thing into the exhaust system, probably close to the actual header pipe. Is there any ideas of where this thing should be best located? See the pix...

Near the collector is best. the wide band sensors are heated, so placement is not as important as it used to be.

For durablity- at least with a slight incline downward. If you can get the sensor totally vertical, awesome. But it's also normal to the gas flow. From the collector- it's best to be 2-3 pipe diameters down from it, for best mixing.

Closer also means shorter time constant, or transient delay- so it's easier to identify the reason why you are not hitting your target.

I would put that heat shield off and have a peek under, there may be a o2 bung that is plugged, there already

Thanks everyone. I have a much better grasp of what to do now.

Here is the update. The metric nut fits my O2 sensor, has been cut and welded it on in a convenient spot. I think it will work and it looks fine.

Cool build! Any other pictures?

Here's a couple

Nice ride. Lot different than the old five and dimes.