Customize column of the region fragment (Document table)

Hello,

I would like to costumize the document table : I my organisation, it doesn't make any sense to have the column
"Cycle Life", "Author" and "LiveEdit" (the last 3 colomns). I've found where these 4 files are defined :

/opt/NUXEO/server/default/deploy/nuxeo.ear/nuxeo.war/incl/document_table.xhtml
/opt/NUXEO/server/default/deploy/nuxeo.ear/nuxeo.war/incl/document_table_simple.xhtml
/opt/NUXEO/server/default/deploy/nuxeo.ear/nuxeo.war/incl/document_table_trash.xhtml
/opt/NUXEO/server/default/deploy/nuxeo.ear/nuxeo.war/incl/document_table_with_popup.xhtml

When I erase the definition of the 3 columns, they still appears anyway... How can I do it ?

Is it possible to add some ? Like the document size ?

Thx :)