Inish Island just stuck his head out close home to prevail in a protracted duel with Crocus Bay in the concluding bumper at Clonmel.
Testing conditions took their toll in the last as the pair toiled in the ground down the straight.
Robbie McNamara conjured just enough in the dying strides to settle matters by a head.
"That was a slog! I never saw two horses finish so slow," said winning trainer Dessie Hughes.
"We'll go back hurdling with him now. He ran well on his first start over hurdles and his second run was probably even better. It was a hell of a good race that So Young won.
"He might go to Leopardstown over Christmas or could run on New Year's Day.
"He's owned by the Flanagan family from Kildare who also had Grangeclare Gold and Grangeclare Lark with me."
