I have bought Cf landing gear from hobby king for my phoenix extra. These are the 28cc variety. Earlier I had got the20 cc ones but used them on my us40 as the part where the axle mounts is not too wide

Now, to use the 28cc ones I have 2 concerns- firstly the part where the axle mounts still feels not wide enough- i.e. in a hard landing the axle may twist or shear off. Secondly, when tightening the axle, the washer tends to grind into the CF surface. How do I avoid these two problems?. should I sandwich the surfaces which receive the bolts/axle between MS flats, may be 0.5mm thick?

ameyam