it's perfectly safe, however you'll need two monitors to do it.
A better idea is to get Voodoo2 because it uses a passthru cable, and allows you to use only one monitor. Voodoo2's are cheap, and can be had for $20us off of http://www.ebay.com
. And if you buy two Voodoo2's, you can use SLI mode which makes them perform even faster.
And yes it'll work with your GF2. Voodoo2 work with EVERY card I know of, even newer ones like Radeon8500 (yes I tried it)