[allincuddy]

I think you should go metal, an overflow or spill will make the wood take off or twist and over 8 feet x 4 feet a slight twist can put your tank out 1/4 inch from end to end, and from what I have been told anything over 6 feet you better make sure your bang on and stay that way. Just my 2 cents, but I would do it once, spend the money and sleep well every night.
Those stands that you see at revy and home depot, I use those in my fishroom. I bought a 8 foot long x 2 foot wide and 6 long with 2 shelf brackets for 200.00, bet you could get a 4 foot wide for 250.00 and you could park a bus on it.
Mark