You're certainly doing your homework. For user-friendliness, the OS engine can't be beat, and the LA series is fine for your project. You won't need to run this generator for hundreds of hours, right?

Don't be too dependent on the manufacturer's specifications. Maximum horsepower is often calculated, based on tests at much lower RPMs. They find the peak torque, then calculate the horsepower based on the theoretical maximum RPM the engine can turn. That .6HP figure is not obtainable. Realistically, that engine is only capable of about half to 2/3 of that.

Glow fuel makes for awful expensive electricity