Not sure how you would get the nulls to deserialize back into C#. I would do some experimentation with the different XML options. For example, what happens if your orch returns an XML that omits the field? What happens if it returns an XML where the field is there, but with no value (<CurrentGrossRate />).
No, it wasn’t a tag-your-it. I like to use my dog as my picture, because she is much better looking than me[:P].