Use SearchWP in conjunction with Dave's WordPress Live Search. To utilize, add the following to your theme's functions.php and save yourself the trouble of editing the plugin files.

gistfile1.php

<?php

function my_searchwp_dwls_alter_results( $search_results, $deprecated, $daves_live_search ) {

	global $wp_query;

	if( class_exists( 'SearchWP' ) ) {

		// remove Dave's pre_get_posts
		remove_action( 'pre_get_posts', array( 'DavesWordPressLiveSearchResults', 'pre_get_posts' ) );

		// set which search engine you'd like to use
		$search_engine = 'default';

		// set up custom posts per page for Dave's Live Search
		function my_searchwp_posts_per_page() {
			return '10';
		}
		add_filter( 'searchwp_posts_per_page', 'my_searchwp_posts_per_page' );

		// perform the search
		$searchwp = SearchWP::instance();
		$query = isset( $_REQUEST['s'] ) ? sanitize_text_field( $_REQUEST['s'] ) : '';
		$search_results = $searchwp->search( $search_engine, $query, 1 );

		// Dave's uses the $wp_query global so we need to force our results
		$wp_query->posts = $search_results;
		$wp_query->post_count = $wp_query->found_posts = count( $search_results );
	}

	return $search_results;
}

add_filter( 'dwls_alter_results', 'my_searchwp_dwls_alter_results', 10, 3 );