Hi BlueRanger,
Here's the thing: Isolate. (Just as Doug suggests)
I love DIY projects, but there are times that proprietary products are very difficult to surpass.
You don't have to go through a lot of trial and error. You don't even have to learn manufacturer's specs. The Vibraplane that I bought works tremendously well.
My audio buddy around the corner has one, and has gone to the extra lengths to mass load the VP with a 1" thick steel plate. The difference between loaded and unloaded was very substantial. In my estimation it was worth the trouble, and I have to help him every time he moves his TT, the steel plate and VP, so it must be worth some Serious Sonic Benefit.
When time and finances allow, I will buy a steel plate to mass load my VP-TT. You may need to evaluate what supports this combination, because the VP is 150 lbs, the ballast is 140 lbs or so, and then there's the TT's weight to consider. My stack weighs over 500 lbs. Make sure your rack and floors can handle it.
If you want to see what the results are like, without spending $2500, buy a piece of slate (granite rings) 2" thick and two bicycle tires. Half inflate the tires and place them under the slate. Level the TT, level your arm, level your headshell and listen to some of the most wonderful improvement you may ever hear in your system.
In future, consider contacting the Forum BEFORE you begin collecting materials for a project. It could save you time and pain in the wallet.
Keep us posted. You're headed in the right direction: Isolation is a beautiful thing. It would be great to hear what you learn as you progress.
I have no relationship with Vibraplane, nor with Sound of Silence (Steve Klein's business that sells VPs). Steve has been a very gracious host and helped with my VP, even though I owned it before meeting him.
The idea for slate and bicycle tubes came from an isolation sales rep who took pity on a penny-pinching audiophile. When in grad school his class tested all the isolation devices then available. He said 95% of the results could be had with the setup suggested above. Either way, you win. Go to it!
Very Best of Luck to You,
David