A rectangle around subreport brings in extra whitespace at the bottom of the detail band

I want to surround a subreport with a rounded rectangle, the jrxml source of detail band is shown below:

<detail>

<band height="6" splitType="Stretch">

<property name="com.jaspersoft.studio.unit.height" value="pixel"/>

<rectangle radius="10">

<reportElement key="" stretchType="RelativeToTallestObject" x="0" y="0" width="565" height="5" isPrintWhenDetailOverflows="true" uuid="313268d9-3fb3-444c-922b-47c967b643e0">

<property name="com.jaspersoft.studio.unit.x" value="pixel"/>

<property name="com.jaspersoft.studio.unit.y" value="pixel"/>

<property name="com.jaspersoft.studio.unit.height" value="pixel"/>

</reportElement>

<graphicElement fill="Solid">

<pen lineWidth="1.0" lineStyle="Solid" lineColor="#652D86"/>

</graphicElement>

</rectangle>

<subreport>

<reportElement mode="Transparent" x="0" y="0" width="554" height="5" isRemoveLineWhenBlank="true" isPrintWhenDetailOverflows="true" uuid="37df43d6-fb57-4ff1-97cb-6389f9bda634">

<property name="com.jaspersoft.studio.unit.y" value="pixel"/>

<property name="com.jaspersoft.studio.unit.height" value="pixel"/>

<property name="com.jaspersoft.studio.unit.width" value="pixel"/>

</reportElement>

<parametersMapExpression><![CDATA[$P{REPORT_PARAMETERS_MAP}]]></parametersMapExpression>

<subreportParameter name="ORI_ACCT_ID">

<subreportParameterExpression><![CDATA[$F{ORI_ACCT_ID}]]></subreportParameterExpression>

</subreportParameter>

<subreportExpression><![CDATA["/Sub-Template/dms_company/mul_charge_company_detail.jasper"]]></subreportExpression>

</subreport>

</band>

</detail>

and here is the design:

The problem is , there's always extra withespace at the bottom of detail band when it overflows into next page, as you can see here:

How can I remove the whitespace?