How to set margins in a subreport using DynamicReports?

Question

The problem is that the subreport gets the margins of the parent report. The sub report contains an ImageBuilder, which builds an image of a static PDF-file. This image is placed between the header and footer from the parent report. I first set these margins in the parent report:

final MarginBuilder PAGE_MARGIN = margin(20).setLeft(50).setRight(90).setBottom(15).setTop(40);
reportBuilder.setPageMargin(PAGE_MARGIN);

I then try to set small margins in the sub report with MarginBuilder, but it does not work. How can I make this work, so the subreport does not get the same margins as the parent report? Here is my code for the sub report:

private void createImage(final JasperReportBuilder parentReportBuilder, byte[] contentOfStaticPDF) {
    JasperReportBuilder reportBuilderForSubreport = report();
    final int PAGE_WIDTH = 450;
    ImageBuilder imageBuilder = cmp.image(getContentAsInputStream(contentOfStaticPDF));
    imageBuilder.setFixedWidth(PAGE_WIDTH);
    imageBuilder.setStretchType(StretchType.CONTAINER_HEIGHT);
    MarginBuilder marginBuilder= margin();
    int margin=1;
    marginBuilder.setLeft(margin);
    marginBuilder.setRight(margin);
    reportBuilderForSubreport.setPageMargin(marginBuilder);
    reportBuilderForSubreport.detail(imageBuilder);
    reportBuilderForSubreport.detail(cmp.pageBreak());
    SubreportBuilder subreport = cmp.subreport(reportBuilderForSubreport).setDataSource(createFakeDataSource());
    parentReportBuilder.detail(subreport);
}