Currently this is not possible as an administration option with the xoops2 versions. It can be achieved by modyfying the theme.html file so as to position one of your blocks beneath the page content. I personaly used one of the center-right blocks as I was not using it anywhere else.
In future releases of XOOPS this feature is planned to be implemented as an administration positioning option so there will be no need to alter theme files.
Ans:
Thanks for your answer.