I followed the "third option" in the instructions at: http://docs.joomla.org/Make_a_Section_Menu_Item_drill_into_a_Category_Blog_layout
and the results are as expected, except... when I drill into a category to see the blog layout... the articles are in a single column for the first article, and then it's two columns after that... and it's a single column template so the stories show up over the border and make a scroll bar at the bottom.
I then tried to fix this by changing the default "num_columns" in everything under "com_content" to "1" instead of "2"... this didnt do anything as far as I can tell.