My son got hit by an x-factor last summer... He didn't think it was funny... I laughed after I realized he was ok.... Almost did a 360 in the air... Needless to say, he doesn't stand in the path of trucks anymore.... As for hitting myself... Yes I've done that several times... It happens... sometimes I just misjudge the stopping distance...
I don't find myself replacing any more parts with the os 18 engine than I did before, just have to be more careful during the setup and gear alaignment.