Unfortunately, there isn't a function that you can use like in Atahualpa to position something after a certain post. However, it's not that difficult to move it around using jquery.
First, enclose the widget area that you've defined in a DIV, and give it a class called Ads_Widget, like this:
Code:
<?php bfa_loop( 'postformat' ); ?>
<div class="Ads_Widget"><?php dynamic_sidebar( 'Ads_firstpost_widget' ); ?></div>
<?php bfa_content_nav( 'multinav2' ); ?>
This will make it easier to select in the jquery code.
Then go to Appearance > Montezuma Options > Head > Insert Code. This section is useful for putting in javascript. If you track your site statistics using something like Google Analytics, for example, this is where you'd put it as well.
In the Bottom field, add this:
Code:
<script>
jQuery(document).ready(function($){
// Make a copy of the Ads DIV and insert it after the first post
$(".type-post:first").after($(".Ads_Widget").clone());
// Remove the last ad widget from its current location
$(".Ads_Widget:last").remove();
});
</script>
The jQuery ready function executes after the document has been loaded.
There are two lines in the function, both of them commented. The first makes a copy of the ads widget and inserts it after the first post. The second line removes the original (i.e., the last) copy of the widget from the bottom of the page.