At 11th level, a paladin's mount (if he took one) gains the celestial template. Most of it is straight forward; it gains darkvision 60ft., it would have 9 HD at the time, so it would gain resistance 10 to cold, acid, and electricity, and DR 5/evil, and gains smite 1/day. That's all straightforward enough (though if I've misconstrued anything, please don't hesitate to speak up.)
Then we get to the part about Spell Resistance. The template says that the creature gains SR='New CR'+5. Well, what would the CR of an 11th level paladin's mount be? And would adding the template increase it?
I would think that an appropriate SR would just be the paladin's level +5, as four levels later it becomes paladin's level +11, but I can't find anywhere that it makes the destinction.
If there isn't a rule for this, fine, I can accept that. I'm mainly asking; Does anyone know of a ruling about this, and if so where I could find it?
Beyond that, if anyone has any suggestions, or notices something I missed or messed up regarding this topic, I'd be obliged if you'd let me know. That said, I am primarily looking for a ruling.