When I last got PPG certified in 2007, PPG said no bigger then a quarter. Any bigger and you should spray a light coat of epoxy. As for spraying epoxy over filler primer, yes its fine, epoxy can go on top of about everything other then etch primer...Eric

Currently working on custom metal and How to videos.

1949 and 1972 chevy trucks
70 chevelle SS455
Pictures of my work and projects
http://community.webshots.com/user/sevt_chevelle