Don't take this the wrong way (although you will probably anyways) - I'm just trying to play devil's advocate here.
I personally think your tests are borderline unusable...
As objective as you were trying to be, the test conditions are way off versus their real world application.
You're missing pressure in these tests, and heat exchange simulation is not quite applicable.
If you had used a heat exchanger, then the results would be more digestible.
I dunno if the tech has changed, but back in the day when all of this stuff first started coming out, the major additive was DETERGENT.
Detergents have the desirable properties of being a surfactant.
http://en.wikipedia.org/wiki/Surfactant
To combat the "foaming" nature of detergents, an anti-foaming agent is added to combat the bubbles.
This was the basic formula for these cooling additives.
It's a reasonable assumption that Royal Purple's Purple Ice would be a bad choice due to the amount of bubbles it produced, but compared to what baseline?
If you added another test where you use off-the-shelf (dishwashing) detergent (and water) and tested how long the bubbles lasted...
I'd put money the Purple Ice would beat that detergent by a wide margin?
This is what I mean by baseline.
Side note, I dunno why you would claim the Ford coolant is the best.
I'd be suspicious of anyone recommending to put ANY Ford part into my cars.
When I was doing my research on the subject, Mercedes Benz type coolant came out on top.
Try do a search on Mercedezs Benz coolant?
-Ted