Anyone know if the Woodmaster flex fuel gasifier is a quality choice? It's made in the USA and burns wood, pellets and wood chips. Also says solar compatible. One concern is it says it's made of heavy duty mild steel? What on earth is mild steel?? 100,000btu unit weighs 1,400lbs and 200,000btu unit weighs 1,800lbs, so I'm confused. Anyone have experience or knowledge about these units?