I have had that problem with the C-Hubs set screw but it was my fault. I stripped the C-hub out with the set screw because I just didn't notice it was tight against the pivot pin. To help prevent against this do as Butter suggested and dremmel the pivot pin and then place a drop of CA on the setscrew. The arm slop I just use a single .05mm washer to tighten everything right up, also when I screw down the suspension brackets I push them together to help tighten them up. There is enough slop simply in the screw holes to make them a little lose. Just make sure in the end to double check that nothing is binding.