all that screw does is hold the very tip of the arm together... it's not like.. load bearing or extremely important. It's a perfectly acceptable screw that was designed specifically for it's use, I wouldn't go changing out stuff like that. It's doing the job it was designed to do and tolerances in that area are super close... for example if you put longer screws in the 4 holes that AREN'T highlighted out at the end off the arm even by a few mm you can ruin the motors.