som random thoughts ....
- lousy WAF - I think others have said this
- try it, its cheap
- fill the holes with sand - messy, but it will deaden it for sure
- a company in Toronto sells rubber/cork/rubber blocks pretty cheap - I can look them up if you want
- go to your local kitchen counter store and get them to cut a piece of leftover granite to your spec - then sit your TT on it - could also make a sandwich or granite/rubber/leftover wood - I used oak
- I ended up with Lowes shelf brackets - 100lb rating/bracket - used 3 lag bolts into the stud for each bracket - 2x leftover 3/4" plywood - TT sits on granite on the plywood - works for me - YMMV - my TT is a VPI Prime
- I was not expecting the sound to be as good as it now is - instruments are now clearer and more 'air' around them - I just wanted to eliminate footfall stuff - my basement floor is concrete + some plywood/resin thing I found at Home Depot + 3/4" solid oak strips - so its pretty dead anyway
- you didn't say what your floor is?
Anyway, good luck with your experiment. I would try and shelves first and blocks second, FWIW.