Is ballast that is not permanently attached to the glider allowed in order to bring an individual glider up to the 3.0g minimum weight?

Yes. If ballast falls off during the flight, timing will stop when the ballast touches the ground. Ballast does not need to be permanently attached. If the event supervisor feels ballast changes, repairs, or other modifications have potentially made the glider over or underweight, the glider should be reconfirmed prior to any remaining flights.