The largest distance of any focus point from {HEAD ~ the best fit surface} is then identified and compared to {TAIL ~ a predetermined maximum distance value} 
The largest distance of any focus point from { HEAD ~ the best fit surface } is then identified and compared to { TAIL ~ a predetermined maximum distance value }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL