For short sleeves, I've gone to UnderArmor Tees for bare essentials, and either Guide Series or Columbia Sportswear synthetics. There are hazards associated with wearing synths around ignition sources, but for the most part, the UnderArmor stuff works pretty darned good under 40 lbs of body armor in 120 degree + environments.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)