I have tried "auto" and it works pretty much as the S-TTL.
This idea of adjusting the internal camera flash output down to 1/128th is great. The internal camera flash recycles so quickly that it gives you more flexibility with improved camera response- shifting the lag time to be a condition of stamina of the cells powering the strobes, the memory card's writting speed, number and frequency of exposures taken in rapid succession and type of image quality settings, rather than just waiting for the internal flash to recycle.
The challenge I have is that as soon as I manually lower the internal camera flash output from 1 to 1/128th or any value under 1...down the Inon strobes output light goes, and the images turn out underexposed.
I am speculating this can be solved by setting the Inon stones to manual, turning off the Inon pre-flash sensors i.e. (bottom right button pushed and locked in) and adjusting the output intensity (upper right knob) until you get a feel for how much light you need based on shooting conditions. If you are shooting balanced or un balanced images ect.ect. the gun number divided by distance to subject or f-stop and getting a feel for how they respond and checking histograms too.
At least for me, the Inon manuals are so tough to read that seems like when working with a fiber optic connection, mastering any type of Inon strobe settings other than S-TTL, TTL, Auto requires pretty much developing your own.
I use the fiber optic setup and like Inon's S-TTL, and want to switch to fully operating the strobes 100% manual, just cant get a hold of a go manual that expains all the settings in sufficient detail for ease of transition. May need to do the trial en err. method and develop a feel for them.