The Beautiful Desert

This is my first grow in a desert environment (which I am LOVING!). I’m using breathable 50 cent reusable shopping bags, that I would judge are holding 4.5 Gal of unamended soil-less potting mix. The humidity here (Southern New Mexico) has been around 10%-15% since I got here. Am pouring gallon after gallon of water in the bags, going for a wet/dry cycle. The darn things will dry out overnight. My overarching point here is that this is going to be more akin to a ‘flood and Drain’ hydro-p. system. Which I predict is a very good thing. It would take someone really dullwitted to overwater, and the roots will be getting a lot of air to them everyday. Flushing will be a breaeze. My only indoor experience is in the Midwest. Humity so high all year round ity would choke a goat. 24 hours after a gooid watering, the mix is airy and light as can be.
This going to be fun.
I saw something on another site that I had never seen. Cut the bottom of a College Kegger Kup, transplant the seedling/clone into that, have filled the bottom of the outer 5 gal. pot with that coconut stuff? Or perlite? At any rate, you water only within the cup, and the guy writing the article claims that the plant will ‘sense’ the moiisture at the bottom, and race down there, thereby creating a bigger, healthy-er root system. If you have experience with this technique, please share? Thanks!