I've got a F27C Stryker PNP, and after about 4 flights, the stock servos are still working fine. I've not had any "hard landings" with it, though! I'll probably end up upgrading to HS-81MGs in the future. I have an older F27 Stryker (original brushed version) that I upgraded to the F27C brushless power system, and I've got the HS-81MGs servos in it. Those servos have suvived a couple crashes unscathed.