yea it's easy enough. And that info on the Saab board is pretty damn good.
The same thing goes for the coolant overflow tank. 50antifreeze/50 water.

Where can I find the specs for the cooling capacity for a 5th gen?

 

Just fill the radiator to the neck with the 50/50 mix and when it starts to overflow into the bottle, fill that bottle to the line depending on if the car is hot or cold. Just fill and turn the car on and take off the radiator cap and you'll see the level has dropped abit so just pour some more into the radiator until you can't put anymore in it. That's your capacity :fawk:

 

it's cheap enough... go with the Dealer coolant for peace of mind.