Dynamic filtering an XsltListViewWebPart

I want an XsltListViewWebPart filtered based on some custom metadata derived from the current user. Following Claudio Brotto’s article http://blog.claudiobrotto.com/2012/extending-base-xslt-web-parts-with-custom-control-bindings , I created a web control that returns a caml query fragment containing my dynamic filters. I added then a parameter binding which modifies the original caml query adding this fragment to it.

The filtering seems to work but I had now two problems: - The heading column filters don’t work anymore - The element group counter is correct but when I expand the element group list the items inside are not filtered

The query fragment result from binding is:

<In><FieldRef Name='Title'/><Values>
  <Value Type='Text'>MP016</Value>
  <Value Type='Text'>MP150</Value>
</Values></In>

        <WebPartPages:XsltListViewWebPart runat="server" .......>
    <DataFields/>
    <ParameterBindings>
        ........
        <ParameterBinding Name="CAMLQueryValuesCodiciPdv" Location="Control(CamlQueryPdvFilter1,Caml)" DefaultValue="&lt;IsNotNull&gt; &lt;FieldRef Name='ID' /&gt; &lt;/IsNotNull&gt;"/>
    </ParameterBindings>
    <XmlDefinition>
        <View>
            <Query>
                <GroupBy Collapse="TRUE" GroupLimit="30">
                    <FieldRef Name="pippo"/>
                </GroupBy>
                <Where>
                    <And>
                        {CAMLQueryValuesCodiciPdv}
                        <Or>
                            <Eq>
                                <FieldRef Name="pippo"/>
                                <Value Type="Text">bolla</Value>
                            </Eq>
                            <Eq>
                                <FieldRef Name="pippo"/>
                                <Value Type="Text">fattura</Value>
                            </Eq>
                        </Or>
                    </And>
                </Where>
            </Query>
            <ViewFields>
                <FieldRef Name="pippo"/>
                <FieldRef Name="LinkTitle"/>
                <FieldRef Name="plluto"/>
            </ViewFields>
            <RowLimit Paged="TRUE">30</RowLimit>
            <Aggregations Value="Off"/>
            <Toolbar Type="Freeform"/>
        </View>
    </XmlDefinition>
</WebPartPages:XsltListViewWebPart>

<GS:CamlQueryPdvFilter runat="server" id="CamlQueryPdvFilter1" ColumnFilterInternalName="Title"></GS:CamlQueryPdvFilter>

How can I resolve this?