Seshat; Goddess of Wisdom, Knowledge, and writing.
if I'm going to go outside, I like putting things into a tiny tree bag (8 x 10cm), then into a full sized tree bag (18x22 cm), then eventually into a gallon airbag of various size, putting one into another, into another, and let the roots simply go though the bags....What is the purpose of the pot inside of the grow bag? I have seen this many times ...just wondering what purpose it serves?
That way, as the biome develops it fills out the layers in between, making the likely hood of disease, infestations, pathological fungi ect... more difficult to penetrate to the core. Protecting that stump with layers of fabric, and symbiant microbes. Even a cloth top cap would be useful in this regard, and it would probably hold the moisture a bit better, possibly.
Anything that protects and encourages root health, I take every precaution possible. I'm a nut about healthy roots. I've had roots fail, and leaves fall off the plant in the past, drastically reducing yields. Especially during transition of flowering. Promoting a good bio layers is fundamentally key in the outside environment IMO.
Also, I like drying my pots out completely, and good fungi development keeps the plant highly inflated, even when there's virtually no water in the pots. I've had plants stand erect in pots for an entire day sometimes without water, but still be standing tall.
I'm certainly not suggesting to allow the plants to go dry for extended times on a regualr basis, because that does inhibit growth to some extent, especially in the earlier phases, but once I get toward the end, I do lots of dry stressing. That's when you need the fungi the most, and it's usually when the fungi are struggling. Phosphate really is a killer of your biome, and it's really important to regulate that mineral carefully during the flip, and keeping things healthy going forward, because bud development is greatly increased by a healthy Rhizosphere.
Substrate is a universal thing above all else we can readily manipulate.