for me, the difference between [ambient temps of] 95* and up vs 95* and below is pretty big. seems to be some sort of threshold. i run 200* pretty easy in traffic with it around 110* outside. 170-180* below 95* outside. just my experience.
remember that the less temp difference there is across the coil, the less cooling can occur. the rad will cool more degrees if it is receiving 70* air (ambient) while running at, say 180*, than it will if the ambient air is 110*. less delta means less absolute cooling. not much one can do.
anything over 178 at the ECT should get you into closed loop. in the old days, guys ran cool - they wanted hot oil and cold coolant. with EFI, you cant run so cold. it is said that you want the oil between 200 - 230. the exact temp is often debated. over 250 with dino oil is not good - it breaks down pretty fast. EFI 5.0's tend to keep the oil on the hot side - not uncommon to be over 250*. oil coolers are nice.
it is also kinda surprising how little coolant helps with the boiling point/freeze point. every little bit is crucial, but coolant does not help as much as one migh think. of course, if we all ran at perfect temps, there would be no worries. but if you run straight water and then have a glitch, there is no safety margin. although some do run straight water, with perhaps a WW type product and some corrosion/lubricant type product. i would not on a street car.
Hazmat, what i might recommend for mixture recommendations for others: try to run 50/50. if a little too hot, try 65/35 or 70/30. i try to recommend that people run as much coolant as possible (for glitches, as above). keep thinning it down till it runs where the person wants it. everyone's systems are a little different and some can get away with less heat transfer (more coolant, less water) and still run the same temps as someone else with less coolant. good info though - your theory sounds nice to me. i would just not necesarily jump right into such a low amount of coolant unless necessary. i bet changing the coolant twice a year kinda sucks though.
a lot of this was just general info i thought might kinda help - comments were not directed at anyone's posts or comments.