Zu Soul Superfly

Yes, I do :)

If I am not mistaken the requirements for floor to speaker gap with the Superfly is different from that of the druid as the pyramid shaped cartridge and finger slots at the bottom of the cabinet performs the bass tuning . Do not have manual with me , but I believe the only requirement re the cabinet to floor gap is that it allows proper function of the griewe loading system. Is it possible that you have lowered the cabinet too close to the floor interfering with the bass loading system ?

If the SF is like the Omen, the manual says as long as you can slide a standard CD case between the speaker and the floor you're fine.
If you're using the carpet spikes I believe the gap will be greater than 1 case, but the way I interpret the instructions that is OK. If you use the bare floor studs and not the carpet spikes you can get the gap lower than 1 CD case (on bare floor) up to more than 2 cases.

FWIW - I found that gap to be a pretty big adjustment knob. I have my Omens on boards with the carpet spikes.

Can slide two CDs under the speakers. Definitely not too low. As stated previously, too high if anything. I thought Phil Cobra had something to say about this. Also, as said previously, I had the bass and then it went. Nothing changed beyond temperature.

The loading on the bottom of the speaker is critical IME. If incorrect, you simply are not getting all the bass the speaker has.