not sure that it says anywhere that you can or can't, but from my understanding the very essence of a template is that you either have it or you don't meaning you can't have the same one more than once.
BUT since you GM is letting you bend the starting rules to begin with, I'd say it's his/her call on what he intended by letting you have +2 CR. :)
This wonderful little tool allows you to even implement advanced and giant 3 times each and I've been using it to great effect and without problems. Of course you need to use a little bit of common sense with what you're doing with it, but advanced x2 works just fine. It's just a template, after all. Nobody is going to run around in the world and say "hey, that is an advanced ogre". They are going to say "damn, this ogre is tough!"
And if they meet one that is bigger and a LOT tougher(advanced 2 giant 1), where is the problem?
Works just fine.
Just stay away from incorporeals and the young template. That's a TPK-machine.
Edit: Just realised that you don't seem to be the GM, so if you want to be really cheesy-powerful, make a spellcaster advanced 3 young 1. That nets you a CR+2 that is just beyond powerful ^^