XRAY - Model racing cars

Hi, I am having a few issues that need help with while building my first XB8

1. The rear arms are binding once fully assembled? My solution would be to sand the 2mm shims down to 1.8mm to free this up. ( arms are free if I loosen the mounting screws 1/4 turn)

2. Servo saver - Manual states to have 4-5mm of the thread sticking out the top once you thread the top on and tighten down the spring, The maximum I can get is 2.5mm down and it is extremely tight already that I would need pliers to tighten it further. Is this correct as I have checked everything correctly installed. Can I leave it at 2.5mm and test once the car is on the track?

Thanks
Deon

i run my servo saver at 2mm on high grip track and its fine,5mm broke servo for me,
hinge pins should be ok with screws 1/4 turn loose just make shore the pin does not bind
in the arm as they are tight as new.