Just to add some semi objective information to this debate, I've attached the Mil Spec guide to installing a 2A042. From a quick look, it seems that there are guidelines for the moment of inertia of anything you're going to bolt on it directly. Plus there is some history with airboats, and there's been at least one ultralight. So I think it might not be quite as problematic as some potential installations. The specs say "Maximum horsepower at 3600 rpm" is 16.7, so things may not be quite as bad as they seem. They also say "maximum elevation for rated power" of 5,000 feet. And a maximum operating temperature of 120 F. So I'm thinking that means you can get at least the 10 hp under the implied hot and high condition. It's a questionable assumption, but if we assume that denser air means a corresponding increase in power, then that gets us up to 13 horsepower on a standard day at sea level. If we're fortunate, and that also applies to the 16.7 hp, we're up to 21.8 hp! Rumor has it that there's a restrictor plate in there, too. Recommended rpm goes up to 4,000, so perhaps when that restrictor plate is removed...
View attachment 74726 I wonder how much that cooling fan uses up?
What I haven't been able to find anyplace is what a 2A042 weighs when you strip off all that junk it doesn't need in order to fly. Apparently it weighs 150 lbs with all the junk. Seems to me that's the most critical factor. And I'm a bit pessimistic.