You could but there is a decent chance MAS 500 reporting won't work.  However it has been reported that sometimes you can get 2 different versions working on the same machine.  I did it when Crystal 10 then 11 came out.  Try it on a throw away machine and see what happens, make sure it's not your terminal server (assuming you are running 500 that way).  MAS 500 however will not use the new version it will use the old version.