Maybe they’re basing their outlook on ag equipment’s solid performance in the past year. Or perhaps they’re taking comfort in the fact that the farm machinery business wasn’t hit anywhere near as badly in the 2008-09 economic meltdown that their counterparts in automotive and construction equipment industries. But shortline manufacturers exhibiting at the Farm Progress Show earlier this month remain upbeat, though guarded, about their prospects for the new sales year. Commodity prices, they say…