I suppose it depends on the bearing. I know Anderson, and I believe
Nacci bearings come in different configurations; both solid shell and
open sided (to allow passing a mounting post or stand-off). This said
both models use the same "core", which actually holds the balls and
tracks, which can be swapped from one model to another. This indicates
merely having an opening the length of the bearing is not relevant. On
the other hand if there is some residual tension in the metal and you
cut it it may open-up more than you wish and not hold the core tightly.

dennis
in nca