One of the many reef websites had this exact thing discussed in a pretty extensive article. Its not in my bookmarks, but I'll look around and hopefully I'll find it.
For anyone that might remember the article and has it bookmarked, it goes into detail about all sorts of ways to reinforce your flooring and what you need to tkae into account when figuring how much weight your floor can handle.
Found one: ( I lied, it was a cichlid site)
http://www.cichlid-forum.com/article...ium_weight.php