I am afraid the answer to my question will be to abandon the great ease-of-use built into the drag-and-drop dynamic sidebar and widget functionality.
Since my five most recent posts already populate my homepage, I want to suppress the recent posts widget unless the current page is not is_home().
I've tried a bunch of stuff... the most recent (and promising, I muttered to myself in yet another burst of egocentrism) being to surround the three lines near the bottom of wp-includes/widgets.php, inside the wp_widgets_init() function, that mention wp_widget_recent_entries with a
if (!(is_home())){<<three lines of native code>>}
but no go - I get the recent posts box on all pages.
It brings a tear to my eye to have to abandon such an elegant, cool, drag-n-drop functionality soley because of a lack of new documentation... unless...
Do you have a solution?