i wrok on my own stuff on am running a 5 year old fs 74 , the only thing is with a soilid shaft you can run metal blades for cutting woody type brush, where the flex saft won't hold up as well, also if you should ever get your shaft tube bent (and i have done this) you can unbend the shaft and keep on trimming i ran mine kinked for about two weeks until i finnally changed it , a solid shaft would be hard to get by doing that.