once the roots get thru the material, they form fish-bones & grown much like a dwc root...Nice to hear from u Mistress. Yes out the bottom that's ok with me as long as they don't block up the smart-valve but i wont let that happen.
providing a large basin, trough or shallow pond for the roots, once they push thru the material, & as little obstruction as possible, =... so, maybe maintain 1.25-2.5cm of water/solution in the trays encourages root growth outside of the container.