I have yet to see any pesky roots poking their inquisitive tips into the tray, even with 150 cm + plants.
I suspect the "copper" on the root control disk is there to prevent any algea in the tray, rather than containing any roots on the lam.
I just got 6 more pots, only the pots sans tray and valve, idea being to veg 6 plants in those pits and then just simply swap them into the tray/valve in the bloom room. I forgot to order the root control disks, and just to vindicate that thoughtful oversight, I'll cut some root disks from garden variety mulch cover material..... This is what I do with Airpots too........ We'll see.
I just realised, I'm using 25 L XL Autopots, maybe root invasiveness is more of a risk, or possibility if you like, in the smaller Autopots.
Anyways, just for peace of mind and as I don't trust those spill trays tents typically comes with, some homemade trays made from EPDM pond liner, gorilla tape, some grommets and ties, are going in underneath the standard spill tray. That's the same material used for ponds and roofs with a 25 years warranty. Better safe than sorry...... With 200 l of potentially leaking water.....