Two more suspected members of the "hole-in-the-roof" gang, including its alleged mastermind, were arrested yesterday in the record $11 million Sentry Armored Car Courier robbery. Federal agents still were looking for at least two others.

Demetrios Papadakos, 36, the alleged "brains" of the gang, was arrested at his residence south of Miami. Papadakos, also known as Jimmy Patadokas and Jimmy Pappas, is a native of Sparta, Greece, and previously lived in Norwalk, Conn., the FBI said.

The FBI said Papadakos "seems to have the most significant role in the robbery." The $11 million taken in the Dec. 12 robbery has not been recovered.

The other suspect, Eddie Argitakos, 23, was arrested shortly after midnight yesterday in New York, Lee Laster, assistant director of the FBI's New York office, said.

Two other men, Sentry security guard Christos Potamtitis, 24, and George Legakis, 21, an accounting student and part-time cook, were arrested Wednesday.

Laster said the scheme to rob Sentry, the largest cash robbery in the nation's history, was formed in September or October 1982 during a series of meetings at a New York City diner where Legakis worked as a cook and at Argitakos' home.

None of the money has been recovered and Laster said authorities don't know where it is. "If I knew, I'd be out with a shovel looking for it."