FWIW--:-)
I found a Bosch single wire O2 sensor for about $20.00.  Bosch #12013.
Seems to work fine, but we will have to test it over at least 100 hours to
prove it will be worth the cost difference..:-)  Ed, you might get your O2
sensor expense down to $.18/hr. or so..
Tommy James<><

 At $42.00 that amounts to approx 36 cents/hour or about 2 years flying time
at my present rate.

Ed Anderson