[George16]

15 or 16mm will work just the same. There's not much difference strength-wise between the 8x16x5mm against the 6x15x5mm bearings. I'd rather install a pair of setback arms in order to give an additional 22mm of length. It will be more stable and less prone to wheelies and flips.

I have both 15 and 16mm versions of racerx and I can't able tell the difference.

Edit: 16mm racerx is required if you're going to use the 8mm cvds unless you have a readysource of 8x15x5mm bearings.