HOB overflow noise (still)

[greech]

First off, I know that HOB overflows are notorious for noise and maybe I was a bit over confident in thinking that I could make my drain "dead silent" . I know that diagnosing these issues are very difficult if you cant see/hear what is going on. I will try and post a video tonight if that will help. Also, I have googled left and right and still can't really find an answer so I though I would try and solicit some help from the more experienced folks out there.

This is what I am working with:
-40B DT with 20H sump
-eshopps 800 overflow box with 1" PVC drain with 2x45 degree elbows and one union (pvc flows into filter sock)
-Hofer Gurgle Buster in overflow box
-Sicce syncra 3.0 return (currently dialed all the way down). Having trouble verifying the flow rate of this pump at 4' at the low setting.
-Ball valve on return line approximately 1/4 closed

Currently the interal overflow is set fairly high (lower flow/max surface skimming) and in the outer box I have the air line completely removed from the gurgle buster and the water level is above the "bell" (bushing) and about 2/3 covering the PVC end cap but not covering the hole in the cap for the airline tubing (again not using airline at this point). Ideally, should the bell be completely submerged or should it be set so that water just falls over the bell into the exposed drain holes?

I have all but eliminated the gurgle thanks to the gurgle buster but I still have a bit of splashing going on. I started out using a flex hose as my drain line but the PVC was quieter. However, I ended up having to have the output of my PVC drain slighty above the water line in my sump b/c if it was submerged I would get a huge gulp about every 5 seconds.

I have tried so many combinations at this point and am beginning to think this is as good as it is going to get but would love any suggestions. Sorry for the long post.