Paginated RSS feeds. WordPress, I wish I didn't have to do this to you.

gistfile1.php

<?php
// 'page' sets the page number
add_filter( 'posts_where', function( $where, $query ) {

if ( ! empty( $_GET['page'] ) )
	$page = (int)$_GET['page'];
else
	$page = 1;

$query->set( 'nopaging', false );
$query->set( 'paged', $page );

return $where;
}, 10, 2 );