So far a 70/20/10 mix of coco coir , perlite (NOT BIG N CHUNKY), and hydroton has worked well for retention/run to waste ratios for a hand watered show in 10 1 gallon Cylinder pots. In previous shows my buddy has used custom made organic soil similar to ocean forest in chelates and traces and always had better water retention when using any amount of coco esp when aeration balanced out with hydroton.
Peace