src/main/java/org/efaps/ui/wicket/components/modalwindow/ModalWindowContainer.java
@Override
    public ModalWindow setInitialHeight(final int _initialHeight)
    {
        int height = _initialHeight;
        final WebClientInfo wcInfo = (WebClientInfo) getSession().getClientInfo();
        if (wcInfo.getProperties().getBrowserHeight() > 0 && wcInfo.getProperties().getBrowserHeight() < height) {
            height = wcInfo.getProperties().getBrowserHeight() - 33;
        }
        return super.setInitialHeight(height);
    }
@Override
    public ModalWindow setInitialHeight(final int _initialHeight)
    {
        int height = _initialHeight;
        final WebClientInfo wcInfo = (WebClientInfo) getSession().getClientInfo();
        if (wcInfo.getProperties().getBrowserHeight() > 0 && wcInfo.getProperties().getBrowserHeight() < height) {
            height = wcInfo.getProperties().getBrowserHeight() - 33;
        }
        return super.setInitialHeight(height);
    }
Check it the size of the modal window is not to big and reduces it if
necessary.

@see org.apache.wicket.extensions.ajax.markup.html.modal.ModalWindow#setInitialHeight(int)
@param _initialHeight height
@return this Modalwindow