Media

You'd be better off mixing it with whatever soil you use and other things than have 2 layers of different substrate that may act differently to the things you put in it, which could lead to drastically different root zones for the plant to acclimate to. (i think this is why my larger res hempy don't really help much - roots for water vs somethig solid like soil or coco is a different structure / different style of root) anyway, the drainaige will be excellent with some coco mixed. Do some research on the brand.. see if you can find people complaining about poorly prepared coco that was advertised as low ec and buffered. check out some journals here, if they have it listed in the products.. or if a search term finds it.. i guess as a top dressing it wouldnt be a big deal? maybe try one pot mixed and one or more as you mentioned and see if it matters. i think you'd want the extra drainage qualities at the bottom, though, or mixed in.