Run a 120v variac on 240???

Hi everyone,
    I got to thinking again, shame on me, and thought what would
happen if I ran my 120v 20A Powerstat on 240v. It's rated at 2500va
so that would limit me to 240v -at- 10A. There is probably some reason
that I can't think of right now why this can't be done. Right now
ther is no advantage to running this way, but if I got more 10A or
20A variacs this would make it very easy to run higher currents at