I pretty sure this has been done before
in fact I'm sure of it
http://www.killermovies.com/forums/showthread.php?s=&threadid=301074&highlight=Venom+Vs+Carnage
http://www.killermovies.com/forums/showthread.php?s=&threadid=301835&highlight=Venom+Vs+Carnage
http://www.killermovies.com/forums/showthread.php?s=&threadid=291533&highlight=Venom+Vs+Carnage
http://www.killermovies.com/forums/showthread.php?s=&threadid=26227&highlight=Venom+Vs+Carnage