My soaring performance is very much affected by staying cool prior to takeoff. Over the years, I've learned to avoid overheat by allowing lots of time time before launch, assembling the night before (esp. for FNX), and covering myself from sun. That is not enough tho, so this year I'm experimenting with cooling tech. I bought a cold pack for my back:
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and a vest with flexible, freezable water packs you insert:
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I've only used these once, so will report as I go. I keep them in the pilots freezer door in the supply room in the office bldg if anyone wants to try.