Overriding FormUrls and alternative form?

Question

In a content type, I override the forms of the CT :

<XmlDocuments>
    <XmlDocument NamespaceURI="http://schemas.microsoft.com/sharepoint/v3/contenttype/forms/url">
        <FormUrls xmlns="http://schemas.microsoft.com/sharepoint/v3/contenttype/forms/url">
            <Display>/_layouts/mycorp/mycustomdform.aspx</Display>
            <Edit>/_layouts/mycorp/mycustomdform.aspx</Edit>
            <New>/_layouts/mycorp/mycustomdform.aspx</New>
        </FormUrls>
    </XmlDocument>
</XmlDocuments>

it works as expected, but as soon as I defines these forms, I can't create more forms for a list with this content type; for instance, I have a list definition (with this content type) that have :

    <Forms>
        <Form Type="DisplayForm"
              Url="DispForm.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
        <Form Type="EditForm"
              Url="EditForm.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
        <Form Type="NewForm"
              Url="NewForm.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
        <Form Type="DisplayForm"
              Url="DispForm2.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
        <Form Type="EditForm"
              Url="EditForm2.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
        <Form Type="NewForm"
              Url="NewForm2.aspx"
              SetupPath="pages\form.aspx"
              WebPartZoneID="Main" />
    </Forms>

The pages are provisioned, but whether I try to access to newform.aspx or newform2.aspx, I'm redirected to the custom form.

What is the correct way to defines a custom default form url for a content type, but having the possibility to have other view of the item ?