You might want to consider DuctSox fabric duct for the duct system. Allows for low ESP fans, keeps the air velocity low, ducts don't sweat because the fabric breathes, duct support is less of an issue (crucial in metal ducts in a natatorium setting, even stainless supports corrode in pool environment), metal duct corrosion is less of an issue (some metallic connector ducts are still required).
Yep, I had a heated pool in Houston with a ductsox duct on it. 15 tons on a Comaparable pool of that size.
Most of the pool units I see are way under sized. Some of the local hotels like to throw a 3 ton conventional at a unit that size.