conversion: create "id" out of "Id"

Dear All,

another problem during converting a structured FM-document to xml:
In my unstructured FM-docuements I have the fm attribute "Id".
But in the DITA dtd I use the fm attribute is called "id" with a small i.

I have an application just for the conversion from fm to xml.
In the R/W-rules for this application I inserted the following line:
attribute "id" is fm attribute "Id";

Problem is that in the xml I get after conversion, both attributes are set: "id" and "Id".
Right now I have to delete all attributes "Id" manually.
Is there a way to do this automatically and without losing all the cross-refs?

Also: Is there a way to assign the attribute "Idref" to the fm-xref attribute "href"?

Cheers,
Anna