"In one word, it's comfort," he said.
With his build, Peterson said, his thighs fill slacks to capacity, causing chafing and scarring.
Peterson, 48, has Finnish and Norwegian ancestry but not Scottish. He began wearing kilts a couple years ago when his wife brought one back from a trip to Scotland. (A spokeswoman for Britain's Royal Mail said kilts are not allowed as part of its letter carrier uniforms.)
Now Peterson wears them everywhere -- to one son's football games, the other son's concerts, shopping and gardening.
"It's the difference between wearing jammies to bed and wearing your work clothes to bed," he said.
Before the convention in Boston, Peterson spent his family's $1,800 economic stimulus tax rebate to mail about 1,000 letters and photographs of him wearing a prototype Postal Service kilt to union branches in every state, Guam and Puerto Rico.
"Unbifurcated Garments are far more comfortable and suitable to male anatomy than trousers or shorts because they don't confine the legs or cramp the male genitals the way that trousers or shorts do," he wrote. "Please open your hearts -- and inseams -- for an option in mail carrier comfort!"
The union's executive committee recommended disapproval, saying there was not enough demand for kilts to be worth the bother of the resolution, and delegates agreed by a large margin.
But Peterson said there are plenty of approved uniform items that very few mail carriers wear, including a cardigan sweater, vest and pith helmet. He said many convention delegates did express support after his resolution was voted down.
"I got so pumped up after being at such a low that I'm taking this to the next convention in 2010 in Anaheim, Calif.," he said.
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