BP, are you cooking right on the grate or on a stone/steel? I can't post the link, but I've found that a 3/8" baking steel gives consistent results and a nice crust - I like it better than my stone but have never done it directly on the grates.
Try the 3/8" steel - it's relatively inexpensive and I think it does a better job on the crust. PM me and I'll give you the info if you want to give it a try.