Trunk Temperatures II: The Cooler Strikes Back

My first experiment (link) showed that a cooler moderates the temperature swings more than it actually keeps things cool (without something cold inside).

But that left me wondering how much difference freezing the bottles first would produce. Here's the result:
Code:
	Trunk	Cooler 	Outside
M	125/86	33/26	96/72
T	129/78	82/33	94/71
W	132/84	96/82	99/72


The lows are from the night before each high. By Wednesday we were back up to the previous temperatures.

The good news is that the ice did last for about 24 hours, even in a trunk with the sun beating on a glass hatchback.
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Okey-dokey. What's plan B?