Perhaps a bit related ....

When the belt wants to wander no matter what
(happens a bit on some belt snders, as an example)
I found that you can build up a crown with a few turns
of "fiberglass" shipping tape.
It seems to last about forever but may need to be
removed for a new belt.

Might be easier to build up a "crown" (as needed) with something
(a polyurethane based tape might last forever) than to
try to machine it in the first place (& get it right).
--
Cliff