Defining less vars in section

less-vars.php

<?php

  	function section_persistent() {
		add_filter('pless_vars',array($this,'customless_vars'));
  	}
  
// Custom LESS Vars
	function customless_vars($less) {
		$less['ba-ss-thumbs-height'] = $this->opt('ba_ss_thumbs_height') ? $this->opt('ba_ss_thumbs_height') : '341px';
		$less['ba-ss-thumbs-margin'] = $this->opt('ba_ss_thumbs_margin') ? $this->opt('ba_ss_thumbs_margin') : '20'.'px';
		return $less;
	}