New set-up using T5 hanging fixture! And a ? about a heat mat.

[PrognatusAfera]

My dad was awesome and helped me hang this Hydrofarm T5 (from the Jumpstart set) from my ceiling, because the stand it came with was more problematic than useful for my particular context (if I find I need to be adjusting the height more often, then I'll just add a few links of chain to the ends of the lines from the ceiling so I can adjust from the bottom).
I used my light meter to arrange the plants underneath, and it seems to work out alright. I think tonight when I get home I'm going to put some wood or bricks or whatever underneath the wooden tray to raise the mounts (mostly Catts) up a few inches closer.

I also put a hydrofarm heat mat in underneath the black pebble tray, but I'm wondering if it's going to be effective there, through the plastic tray, pebbles, and water. I felt the water in the morning, and it was definitely warm, but not particularly. It had only been on a few hours by then though, so maybe it'll heat more??
What do you think, do I need to take the sweeties out of their ceramic orchid pots so their roots can access the heat? (They're in clear plastic inside there.)