Those fairly crappy bearing holders are just fine on mine, and because they arent machines perfectly to fit the bearings, the 40mm bearing holders on the Nimbus II frame will fit a 42m bearing.
Meaning you can fit any 40 or 42mm hub into the Nimbus II frame. DX, Onza, Qu-Ax, Profiles, Koxx, and KH. They all fit. =p