I might be premature in my conclusions. I am thinking I did not comprehend the tempurture rise to fully open an 180F thermostat (and when to cut off the fans.). I have the fans cutting off when the radiator outlet is 160F, think 20F drop from 180F inlet. while it looks like with 20F rise to fully open thermostat,that would be the seen 200F. so I proably should change the fan switch and consider 200F the operating temp
I just ordered a Tim Myars 160F thermotat and that might be the route I try
But...back to basic.
75F day
180F thermostat (say 100% open at 200F)
both fans running
the fact the coolant goes to 200F (and climbing) indicates insufficient cooling ... period!