If I may add an opinion, I think your core angle should also reflect the polish status on the ball AND the oil pattern on which you want to use it. The higher the polish, generally speaking the safer it is to use more of an angle, like 4x2 or so. With a dull particle pearl, you may want to go no further than a 4x3 UNLESS you are going to use it on heavy oil.
These days particle pearls can come polished, highly polished, matte or dull. All 4 require their own separate processes and considerations.