Here's what the folks over at Firestik told me:
Normally ... metal on the horizontal plane aids the antenna. However, anytime you change the environment around the antenna .. you need to put an swr meter on the set up and retest it because it could change how the antenna performs. If the rack is causing any problem at all ... it will show up on the swr meter ... any thing else is only a guess.
So I guess I'll ground the rack try retuning the antenna and see if I can get the SWR lower and leave it at that.