[valdet]

Ok this is how you do it.

1. Make copies of the two product files: mysqlbackup2.php and cron/cronbackup2.php
2. Add three extra settings to product:
cbu_date2: M
cbu_prefix2: monthly-backup and
cbu_path2: /home/user/my-custom-path/
3. Make this change at mysqlbackup2.php
From

		// File Information 
		$this->DATE = date($this->OPTIONS['cbu_date']);
		$this->PREFIX = &$this->OPTIONS['cbu_prefix'];
		$this->DUMP_PATH = &$this->OPTIONS['cbu_path'];

to

		// File Information 
		$this->DATE = date($this->OPTIONS['cbu_date2']);
		$this->PREFIX = &$this->OPTIONS['cbu_prefix2'];
		$this->DUMP_PATH = &$this->OPTIONS['cbu_path2'];

4. Make this change inside cronbackup2.php
From

   require_once(DIR.'/includes/mysqlbackup.php');

to

require_once(DIR.'/includes/mysqlbackup2.php');

5. Add new Scheduled Task to start at first day of each month and to run it from cronbackup2.php
6. Done

It was too easy once you figure out, but thanks to Paul for giving the hints. Step 2 was key.

I hope someone finds this useful.