If there's too much oil, it's not a baffle issue. It would do it at both sides because those valve covers are the same, no?
I'd try starting it without the valve covers and be ready for a mess... See if one side is definitely getting more than the other.
Have you checked the rocker shaft hold down bolts? One bolt goes into the oil feed for the shaft. If loose, I'm sure it could move oil places it usually wouldn't go. Longshot, but hey..
Don't overtighten them though. If they're past snug, they're not the issue.