Yamaha U1's and double wheel castors

[David Ilvedson]

List,

I've got four new Yamaha U1's with the little hard castors that are 
tearing up the ballet floor in differnent studios.  If I install rubber 
wheels(.which I have done on big uprights many times) will I run 
into excessive height or fitting problems underneath?  Has anyone 
done this?

David I.

They would rather not install a truck as the pianos don't get moved 
much...