You can just replace the /vm folder with a Unix Symlink (created easily via this) that redirects to the drive of your choice.
It MUST be a Unix symlink, OS X aliases do not work for kernel-level programs (such as dynamic_pager, OS X's swapfile management daemon)
This also has the significant advantage of leaving the com.apple.dynamic_pager LaunchDaemon completely alone, meaning you don't need to tinker with reprogramming system files.
Works great with my multi-drive multi-partition Macbook Pro.