Can I use THK Linear rail on its side or upside down?

I had an idea today for a system of linear rails with a ball screw. I was
wondering if it is permissible (read: a good idea) to mount THK rails on
their side or, in my example, even up side down so that the rail travels
back and forth over the two recirculating slide blocks? The rails would be
fully supported so that they would not flex much.

Can I mount THK rails in this way or are they only designed to be mounted
one way?

-Eric