Isolation tables

Kraken

Hi, I've been trying to put together a high quality holographic workshop with a budget of only $400. What do you think of this design of an isolation table? Tabletop: 4x5'x1/4" sheet steel (for magnetic table mounts) on a 1/2" peice of plywood. Legs: (from the ground up) 9x9x9" plastic container 2/3 full of fine dry sand, 1 cinderblock, 2 sandbags, semi-inflated innertube. Any feedback would be great. (also, know any holography newsgroups?)