Just get A couple of master air screw props for your trainer, the things are bullet proof. I'm A total nut about my props and I have sanded them to balance if slight and used spray on them most the time. Just not too picky with trainer planes. I only use the MAS props on them and the ground strikes seems to be no big deal. A ground strike with an APC is another story and most the time it is destroyed anyway. I once trained three students with one MAS prop, it was with me as long as the plane. Once I pulled it to check the balance after countless ground strikes, it was just dandy?? I don't know how or why but it was still good?[8D] Trainers are the only planes I run Master Air Screws on and they work great.