[69hugger]

I'm going to suggest a very easy trial. I know many here will scoff at this... a few years ago I would have too.
But after I did this, my cooling issues vanished. It is simply see what happens if you remove the thermostat (gasp).
I have a '69 Camaro, 534" big block making 700 hp. My cooling system consists of the 1000 hp rated Be Cool rad w/ twin 11" Spals, and a Stewart water pump. The fans are ECM controlled to come on at 190, and shut off at 170.
When I ran a 160 deg. stat, it would run hot (210-220 +) only if stalled in traffic on a hot day, and take forever to cool down when I'd get moving again.
My very old school engine builder kept telling me to ditch the stat. I thought he was crazy. I'd cite every article ever about how doing so would speed up the coolant flow so the coolant was not removing enough heat from the engine, needing pressure in the block, etc. I was chasing all the stuff you are talking about here. Fan CFM, sealing air leakage cracks, water wetter, blah blah blah.
A few years ago, I was beating on the car pretty hard, and the cooling system blew. Coolant exploded everywhere. The engine bay was drenched. Only after detailed inspection did I discover what happened. With that flow restriction, the cooling system had created so much pressure the rear seal on the water pump had blown out.
I finally tried his suggestion. I have not run a stat since. And the car has not seen 200 degrees since. It normally runs almost exactly 100 deg. hotter than ambient. 80 degree days it runs 180. 50 degree day it runs 150. And makes no difference whether I'm on the highway or sitting in traffic with the A/C on.
I know it sounds crazy. I know the experts will scoff at this & cite why it won't work. And it probably won't work in every case. But in 1/2 hour you can try it. What do you have to lose?