Excellent point.... if you mistakenly use the longer screws, you'll thread the tip of the screw down into the motor's rotor winding and possibly short out the motor(s).All I can say is if you take them off PLEASE USE THE STOCK (smaller) SCREWS we have had to many people have motor problems
And I'm not a fan of them
GL!
The string also provides a small barrier in between the guards. I fly with guards and string always. But, then I am using it as an aerial camera, not a stunt chopper