I'm moving to the Bay Area in January from VA. Am I alow to bring my 10+ round handgun magazines if I convert the to 10 rounds only? Thanks.

The modification must be permanent, not just a dowel or limiter. The modification must be performed before entering the state. You can not import the magazine simply disassembled (likely constituted a large capacity magazine kit)

There is no standing definition of "permanent" but DOJ had previously supplied advisement (from an unrelated attempt to change the definition of a "fixed magazine") that a rivet, epoxied baseplate from inside, or welding which requires destruction of the magazine in order to reverse the modification would suffice for permanence.