They're in my refugium which gets the full 'upflow' from my return pump. It's very broad and gentle, but pretty significant, since my return is a throttled back Reeflo Snapper. They are all attached to med pieces of liverock sitting on a bed of chaeto which the water flows through. I can see waste being pulled away, but the flow isn't directional enough to move the mushrooms at all. I believe the flow situation is pretty good for these guys right now.
I turned off the fuge light, so they will only get a bit of ambient light from my main tank lights above.
I might put the yumas onto a dish and then sit the dish on top of the chaeto just so the chaeto doesn't interfere with the yumas in anyway and provide a more stable base for them. Otherwise I'm going to avoid touching them as much as possible.
These were shipped out on Monday. I wouldn't normally be this worried about corals being in transit this long, but they're yumas which have a touchy reputation, so I'm extra paranoid about these guys.