Custom Structured Content Type within a marketplace package.

MyPackageData.xml

<?xml version="1.0" encoding="utf-8" ?>
<module name="Test" moduleID="28949B9F-0383-4C01-8CFA-7B885DD49D56" version="1.0" sqlTableName="MyPackage" featureName="MyPackage">
  <references>
    <reference name="CMS_API.WebUI.WebControls.SimpleControls.dll" />
    <reference name="CMS_API.CmsUI.WebControls.dll" />
    <reference name="CMS_API.WebUI.WebControls.dll" />
    <reference name="Telerik.Web.UI.dll" />
  </references>
  <fieldset>    
    <field name="Text" type="ntext" options="CMSHtml, SaveToHtmlContent" />
  </fieldset>
  <forms>
    <form name="EditForm" type="Edit" isDefault="true">
      <control type="Div">
        <property name="cssclass" value="'sys_dialogueform'" />
        <control type="FieldSet">
          <property name="cssclass" value="'sys_fieldsettype1'" />
          <control type="Legend">
            <property name="InnerText" value="'My test structured content'" />
          </control>
          <control type="Div">
            <property name="cssclass" value="'sys_formgroup'" />
            <control id="Text" type="CMS_API.CmsUI.WebControls.ModuleTextBox">
              <property name="Value" value="#field.Text" />
              <property name="LabelText" value="'My Package Text...'" />
              <property name="ControlInstance.TextMode" value="'1'" />
              <property name="ControlInstance.Rows" value="'2'" />
              <property name="FormSetWidth" value="6" />
            </control>
          </control>
        </control>        
      </control>
    </form>
  </forms>
</module>