For an annual such as cannabis, there should be no need to transplant, IF, you go from a conventional pot to a final finishing RootMaker pot. The air pruning system was designed for perennials, not annuals.
I consider myself an expert in plant training - that means top and bottom people, not just above ground. In order of preference my root tip pruning methods would be:
1. Copper hydroxide paints aka Griffin's Spin-Out or Microkote,
2. RootMaker products
3. Fabric pots (never use them for several reasons)
As posted at my forum at the Riddle site:
Here's an excellent post lifted from another forum on making your own Griffin's Spin-Out. The links are still valid.
Microkote used to be made under the brand-name SpinOut by Griffin L.L.C. until SePRO bought the rights. After the re-branding they added other metals labeled as "nutrients". In my opinion this is all marketing; the roots will be stopped and not absorb anything near the Microkote layer - so really the only active ingredient is the chemical that stops the roots from growing further (this chemical is copper hydroxide which was the original ingredient in SpinOut).
Microkote is pricey ($28 for 8oz). But you should be able to make your own.
1) Buy some dry Copper(II) Hydroxide, this is used usually as a fungus pesticide. Interestingly, SePro stuff can be bought on ebay (http://www.ebay.com/itm/CuPRO-5000DF-Fungicide-Bactericide-61-3-Copper-Hydroxide-SePRO-3lb-foil-bag-/370622313276), this is probably the same stuff they put into Microkote. Other sources are
KOCIDE 3000 (made by DuPont) or http://kingquenson.en.alibaba.com/productshowimg/424951536-200579235/Copper_hydroxide.html.
2) Dilute the Copper(II) Hydroxide in latex paint. The original SpinOut was made with 13 oz/Gal of Copper(II) Hydroxide (source: http://hortsci.ashspublications.org/content/28/5/527.6.abstract). Remember to account for the original concentration of dry Copper(II) Hydroxide in the pesticide bag (this is typically 50%, for which you would add 26 oz per Gal of latex paint).
Remember to read all the instructions on the bag when handling pesticides.
This costs about 10x less than buying the Microkote solution which is over-priced and over-marketed (b/c of those extra additive "nutrients") in my opinion.
Uncle Ben