be careful dux not to do any damage running w.o.t while too lean.
rules of thumb=
Air/Fuel Ratio Limits.------------------- lambda
6.0:1 Rich run limit
9.0:1 Low power, black smoke------- .61
11.5:1 Rich best torque at WOT ------ .78
12.5:1 Safe best power at WOT ----- .85
13.2:1 Lean best torque at WOT --- - .89
14.7:1 Chemically ideal ----------------- 1
15.5:1 Lean light load, part throttle ---- 1.05
16.2:1 Best economy, part throttle ---- - 1.1
18-22:1 Lean run limit

i dont think u will be able to get out side the 14.2-15.2 range because this is the range in which a standard narrow band o2 sensor reads, which wont make bugger all difference,
and i think if you try and trick the computer it will just vary massively while "searching" for its middle point of 14.7
i have a piggyback hooked to my ecu and a wideband o2, and i know that when the ecu cant equalise easily enough into the narrow range it just starts varying massivly and goes real rich then real lean looking for the medium,
so if u set the new medium at say 20% richer it at say .4v it isnt going to read down to -.1v so you still only have the same scale,
in closed loop my car will bounce continuously between 14.2-15.2 the whole time when parked at idle, and accelerating at low throttle positions,
it doesnt settle at say 14.7 like youd think, if it did then yes i think u might be able to adjust it, but its a constant yoyo.
but using ur technique in my mind i think u will be only able to adjust within the range that the standard o2 can read,
are u proposing that ul get it to bounce within a smaller range instead, say 14.2-14.7? for example?

^that was all in my head and i wouldnt of been happy without saying it because i wasnt sure if u got what i ment last time,

feuw what a story.