Thanks for pointing out the error in my code - 3 posts back - numloops get nowhere incremented 
please provide specific code as I can't read your mind
#define NewPingConvert(echoTime, conversionFactor) (max(echoTime / conversionFactor, (echoTime ? 1 : 0)))
add rounding
#define NewPingConvert(echoTime, conversionFactor) (max( (echoTime+conversionFactor/2) / conversionFactor, (echoTime ? 1 : 0)))
Using the sensors in the real world I can't get 1/10th inch results, how exactly are you doing this? Or, is it just a theory you have?
Yes, it is theory to search for what can be reached with the sensors/ code.
You made a good point that the fluctuations due to temperature are large so working in mm makes less/no sense.