Remember you filed the hole very carefully and the WM pearl is a tight fit.
Use an epoxy type glue and while the pearl is in the bezel, apply it.
Put a blob of glue on the back of the pearl and bezel area immediately around it.
Work/wiggle the pearl a little so the glue gets where it needs to.
Wipe off any massive excess, but do leave a bit of a layer to help hold the pearl.
Apply the glue to the sides of the WM pearl and then put it in the insert- wipe off any excess off the insert.
I enlarge the hole with the x-acto blade- just twirl it around til the holes big enough.
BK's old deal was to file the backside of the insert also so it would sit lower in the bezel, hence look more gen like!
Just removing the rep glue/tape and sticking the bezel back in (I used a small amount of clear auto silicone) is enough to get it into gen position.
No need to go sanding, IMHO.