Spike or not to Spike the question is!
My listen room is 16'X24' with arced beamed ceiling with carped covered suspended 2nd floor. I used my Sennheiser condenser Calibrated mike thru real time analyzer + sweep tone generator on a mike stand toward the spot my Wilsons spiked sit on the floor above. MATERIAL USED.
Best results" 1"1/2 Birch 4 ply Rectangle 2" larger foot print the than the SASHA. Then off to the Hobby store. 5#s RED modeling clay(Zero REZ.)
Laid same 1" thick over the Birch. Ran same sweep# 2 Low Feq test. Results 80Hz>250Hz spike down 4db. Upstairs Bach Organ selection and Boston Pops Live in London RCA 6'dia Drum for the first time could now hear it's skin "MORE CLEARLY."
p.s. Not sure if green clay would have proved better?