I'm looking at the intermediate results of the Loudness filter at Overlap 0% now and they are really not good (1 dB too loud for the highs, 0.5 dB too soft for the lows).
The Loudness filter consists of about 20 separate steps, so I'm still looking which step(s) is/are causing this.
Edit: Found & solved the cause of the too soft bass. And... This also affected the Overlap > 0 version - so the next version will have slightly more bass using Overlap > 0 as well
Edit #2: Found what's wrong with the highs as well... Trying to fix it now
Edit #3: That's now fixed too... Upto that point, the 2 versions are now nearly identical (I must add to that that the Overlap > 0 version has changed as well, it's now closer to the v4.22 (I think it has more deep bass etc., I have not measured it yet though).
Unfortunately the sound is still not identical - there's another difference that I need to fix.....
Fix will be uploaded later tonight.