I did Manfred Dickgiesser foam ear plug mounting for my 450 flamewheel quad with APM 2.5 running v2.9.1 and   MPU6K_FILTER = 20.  APM is mounted on a thin aluminum plate with double-sided foam tape.  A ¼" thick plate of Polycarbonate plastic is taped to the bottom of the aluminum plate between the orange foam ear plugs to give added mass to the mounting assembly. The ear plugs are glued to the top plate of the quad frame with Goop.  Seems to work well for controlling XYZ Accel's.  Z data value analysis in an Excel spreadsheet shows a Standard Deviation of 2.02 for continuous 2300 sample points. 

The ear plugs survived their first crash.  I accidently switched into RTL without knowing and flew it into the ground. 

I would have never thought to use foam ear plugs for vibration mounting.  What a cool idea...