Conn, who was a trained doctor away from the track, was contesting the second Roadsports race of the event at the Northern Irish circuit at the time of the crash.
He had earlier won the opening Roadsports race of the day in his Crossle 47S.
The meeting was abandoned following the accident.
In a statement, the club said: "It is with regret that we at the 500 Motor Racing Club of Ireland have to confirm that the competitor who tragically lost his life in the second Roadsports race at our meeting was our member and friend for over 20 years, Dr Paul Conn.
"Paul was from Lisburn. He joined our club in 1996 and during the intervening years he campaigned his Crossle 47S with increasing success.
"In 2018 he seemed to reach a new level of skill and he began to trouble the established top echelon of drivers in Roadsports, winning in the second race of the May meeting.
"Yesterday he had already won the first Roadsports race, against top opposition, and was on course for a repeat in the second race when he had an accident opposite the control tower, on the front straight.
"Because of the location of the incident, our doctors and the Order of Malta personnel were in attendance almost immediately but, unfortunately, Paul succumbed to his injuries at the scene.
"Once again, we offer our sincere condolences to Paul's family, friends, colleagues and team. He will be sorely missed."