My dad made one of those years ago out of an actual Weedeater brand
trimmer. I was there for a visit and he needed me to help him retrieve
a plastic culvert that a storm had washed back into the brushy part of
his woods. He fired it up and handed it to me, and as you say, WOW. I
was knocking down 3" saplings without so much as breaking a sweat. We
cleared a 3' wide 100' long trail in maybe 10 minutes. I'd imagine it
is dangerous as hell, but effective is an understatement!!