Hi Av8r_Sed, that rod end broke on my model III also had approx 300 hrs on the plane, I also feel very very lucky I had done my run up checked the flt controls one last time and gave it full throttle just as the plane was about to lift off I noticed I had no flapron control pulled the throttle off and discovered the broken rod end.
I blame myself about 20 hrs previously I tried taking any slack / looseness out of the control system and ended up tightening the clevis too much causing it to bind when the stick was moved to the limits to would then bend the threaded part of the rod end and it broke. I now make sure it is loose and free before each flt.