I don't run this brand of trimmer, but does anyone who does know the size (width) of the shaft that spins the head? i know you can switch certain gear boxes, heads and accessories between some brands. i'm wondering if a stihl flex cable (or solid shaft??) is the same width as an echo flex cable? a friend is giving me a stihl hedge trimmer head, and i'd like to put it on the end of me echo. i know the redmax version is compatible with echo, don't know about stihl.