You fly an old beat up 1900 with no autopilot every day. You're arguably more proficient at both hand-flying and instrument flying than any modern jet pilot in this country. That said, your jumbo King Air is a much more stable (and much lesser performing) platform than any swept-wing RJ, which typically spends a good portion of a flight in RVSM airspace.

You are safer hand-flying your 1900 than any RJ pilot hand-flying his/her airplane because of PROFICIENCY. You do it every leg every day - jet pilots might, on average, hand-fly 20 minutes per leg.

It may not be a matter of can or cannot perform, but rather one of prudence and safety - after all, "A man's gotta know his limitations".