If you just box in the sides with ply, that will do the trick Irving. It will also give you a rather nice enclosed cabinet for your tooling too. Bookshelves get a very large part of their strength from the usually very thin back panel and they can be loaded well in excess of 300kg :) If I was back at work I could run it through Solidworks FEA package for you but knowing you, you have done your sums on it :)

Regards, Jeff.