mime types / wsrp

Hi all,

I'm trying to display an excel spreadsheet from within a jsp in a portlet over
wsrp.

Whenever I make a request from the consumer, I get the error:

java.lang.IllegalArgumentException: MIME type [application/vnd.ms-excel] is not
supported by the consumer/portal. Supported types(s) is(are) [ text/html 
text/xml  application/xml  application/xhtml+xml  text/plain  image/png  */* ].

and looking at the wsrp request sent over by the consumer, the mimeTypes it says
it supports are: 

<v1:markupParams>
<v1:secureClientCommunication>false</v1:secureClientCommunication>
        <v1:locales>en-GB</v1:locales>
        <v1:locales>en</v1:locales>
        <v1:mimeTypes>text/html</v1:mimeTypes>
        <v1:mimeTypes>text/xml</v1:mimeTypes>
        <v1:mimeTypes>application/xml</v1:mimeTypes>
        <v1:mimeTypes>application/xhtml+xml</v1:mimeTypes>
        <v1:mimeTypes>text/plain</v1:mimeTypes>
        <v1:mimeTypes>image/png</v1:mimeTypes>
        <v1:mimeTypes>*/*</v1:mimeTypes>
        <v1:mode>wsrp:view</v1:mode>

My question is how do I get my consumer to support additional mimetypes?

I am using WLP 10 MP1.