Nice design! I think I'll do mine and add a floor to hold the magnetic ultrasonic sensor on, or at least a strip of plastic with a frame to hold it in the center. I have had a problem getting and keeping the sensor centered.
Thanks!
I printed a pair of these spacer rings and found them to be a bit small. Not sure if it's the Bambu lab problem or your tank's base is slightly smaller than mine. I used some pruning snips to cut each ring which lets it stretch a bit to fit odd / different tanks. They leave plenty of room for the Mopeka ultrasonic sensors underneath.