Arnold, a Gisborne Intermediate School pupil, would be a good chance at the North Island Champs in Rotorua next month, he said.
Charlie Holdsworth came second on trampoline for boys aged 10 and under and combined with Parker Anderson for gold in the synchronised section.
Callahan said Holdsworth had come a long way in the sport and potentially had a big future.
Riker Rolls and Ngature Tahuri both won three medals of different colours.
They combined in the 11/12yr boys for gold in synchronised.
Rolls claimed silver in trampoline and Tahuri the bronze; Tahuri got silver in double-mini and Rolls the bronze.
Taylan Barber and Tegan Hayward combined for gold in the sychronised section for 11/12yr girls.
Arthur Tilghman showed promise in the boys’ eight-and-under group, gaining silver in both trampoline and double-mini.
Callahan said the club’s trampolinists and tumblers were preparing for the North Island champs being held from July 12 to 14.