Where to weld in O2 Bung for wideband

Hi guys, picked up a Wideband A/F gauge and I need to weld in the bung. Trying to figure out the best place to do so. Im running TTI's so cutting into those is out. Right after the collector I have maybe 1.5" until my H pipe. After the H pipe it curves up towards the drive shaft then curves again towards the back of the car. My exhaust is not mandrel bent so in the curves it has some restrictions, but I probably have about 8 inches of straight pipe between the bends.

The only thing the instructions say is at least 18" after the exhaust port, but doesnt give you a max distance. Thoughts?