To go back at the noise problem ive told earlier,

I noticed due the vibirations it had on lower speeds it could be just the glass/heated bed vibirating to much as it has alot of unsupported sides,
I did a heavier item on it when printing, it reduced the noise quiet alot,
So i guessed if downwards force reduces the vibiration with getting it more stabile, Upwards should do the trick as good,

I did some spongye material under the middle of the heated bed, aprox 1x1 inch, and it did reduce the noise quiet a bit,

I guess if you did this in a + pattern (2 horizontal, 2 vertical, one in the middle) it could reduce it quiet a bit.