After intense reading,,,the O2 senors need to be installed above 9 O'clock and 3 O'clock because moisture will destroy sensor quick.
Tapping into the crossover would give you a rough(ruff)(my opinion) average of the two cylinders. If Adjusting carbs evenly(screws and/or jets) one would assume you will achieve accurate A/F ratio off of each cylinder,,,,,,Ideal world?
From reading,,,,,,,,"I" would tap(the bung mount) into each header 1.5" from header bolts.
O2 sensors need to be hot before they start work'n.
Right off the cyl. head sounds ideal.
Buy a POS header,,,,weld the bung mounts.
Test one side at a time at idle and adjust.
follow the "throttle position guide lines for tuning carberators". Found on this web site,,,
Money burning hole in pocket,,,,buy two of the "Inovative" LC-1 kits($300+,,,,each),,,,then,,,you can monitor both lungs(cyl.'s) at same time.
THEN,,,,,,you could mail the system to other members,,,get your money back,,,they could tune,,,and send to the next,,,,and on and on,,,,,,,,,,
Once you have your bike "pegged in",,,,,why leave it on the shelf?
The units i'm looking at are less costly.
Gauge's,,,$69 * 2,,,,O2 sensors,,,$29 * 2,,,,Bung Kits,,,$10 * 2.
High dollar units(Inovative" LC-1 kits) come with software so you'll get more info.