Headers and o2 sensors

[JeepsAndGuns]

So I finally got my headers installed on my cherokee. Now I need to mount my o2 sensors (nb and wb) I am running a heated o2 sensor, plus I coated the headers in techline ceramic coating to help keep the heat inside the exhaust. I seem to remember reading on here a time or two about o2 sensor placement behind a header collector and something about specific distances away from it. The collectors on these seem a somewhat decent length. I bought some flanges and welded me on a couple short peices of pipe for the exhaust shop to connect to. Take a look at the picture and tell me, would mounting the o2 sensor a couple inches behind the flange be a sufficent distance from the coollector? Or should it be further back?