Restore to CF03 between Flasing ROMs?

Right now, I'm using one of Adrynalyne's 6.5 ROMs that I flashed successfully directly after my upgrade to CF03.

If I want to try a different ROM, do I first have to revert back to a clean CF03 by re-running the VZW utility? Or can I just use the UMDL and go straight from Adrynalyne's ROM to, say, one from Lioryte?

BTW, I wanna say Thanks right here for all the effort you cooks put into this. It's fun and make's the Omnia a pretty decent alternative to iJunk.