,...on string trimmers?

Stihl makes a tool called a "Yard Boss" with a 27cc 2 stroke motor. It comes with a small tiller head that I'm not interested in. But it can also be fitted with a string trimmer head that will accept a circular brush cutting blade. The rig has fairly wide set handlebars and can be outfitted with an optional pair of wheels. It seems to me that it would be a good tool for cutting down shrubs and various vegetation without having to crawl around on the ground with a chainsaw.

So has anyone had any experience with a string trimmer equipped with a circular brush cutting blade?,....if so, how well did it work and what size engine was on the string trimmer that you outfitted with the blade?