I have the 39" sump. The controller broke, they said they'd send me a new one. Never got it. So I made one out of an ESP8266, if anyone wants the code and diagram let me know. One advantage is that I can now send out a MQTT message that records when it advances. This allows me to approximate how much is left.
I kind of love the sump, honestly. I dumped my homemade one. I was so sick of filter socks. I think one of the issues I am pondering is can you reuse the rolls by washing them somehow. I hate to just throw them out.... here is a mini map of where the sensors are and such.