No, get out of my thread! ;-)
My plan is to make an option and a button with scope functionality (correct density for selected blocks, correct density in the current the layer and correct them in the whole prefab). Maybe I should add an "Advanced Editor" tab in the option menu including this and similar settings for advanced users. Is that what you mean?
According to Guppy, you have to set a certain negative density value to get rid of the gaps (something between -90 and -99, I can't remember). As far as I remember, he mentioned it in his 'like to build' thread.