I went through this fire drill and this is what I did.
1. New Bergs Radiator and New Water Pump
2. Lost 3/4 gallon on 100 mile tour in very hill conditions.
A. Checked for head gasket leak with radiator test kit... A-OK
B. Added Bill's wonder roofing nail
C. Added 165 degree thermostat.
Runs at 195 degrees on a 95 degree day up hill all day!
Last tour we were running 40-45 up long grades and NO coolant loss!
Part of the problem is the new water pumps really move a lot of water which was getting pushed over the top of the overflow tube. The nail did the trick no more loss.
Also the thermostat slows the flow slightly so not so agitated in the top tank.