Sangii can be pretty huge, I have seen 70-80 cm plants in Sulawesii.
There are 2 funny things about the barbata section, first they like to grow in deep shade, at least the long-lasting ones. In Philippines, where I have seen argus, I noticed that most argus in medium to high light were clearly monocarpic, where huge clumps would form in the shade. The ones in medium to high light had a single growth, and no new growth coming ( and no previous growths as well).
Several species as well never get water from the top, like some populations of hookerae, all the sangii I have seen, and zieckianum. The water runs from under the plants in the sangii colony ( they grow in a peat-like mix, very fibrous and deep, like zieckianum and wentworthianum), and because of the huge trees, water seldomly falls on the ground. This accounts for the gorgeous freshly wild collected plants with pristine leaves (nearly all the sangii straight from the forest looks like the one from the left on the picture, perfect beautiful shiny leaves). On the other side, the RH is extremely high, and at night time water condenses on the leaves when the temps get cool.