I want to raise a workbench up by a few inches, and thought it would be handy to do this usIng suitable braked castors so that I can move the bench around more easily. The legs of the bench are 80 x 60 mm in section and made of softwood. I can't find any suitable castors with a rectangular top plate of the right dimensions, so I was thinking of using castors with a single bolt hole, attached using a 10mm dia screw. This is the kind of castor I'm thinking of:

http://www.rosscastors.co.uk/100mm-s...ber-wheel.html

Would this work? Any better suggestions please.