I have a 5.1 MacBook Pro (5.1 Model Late 2008) with 4GB of Ram. All the apple documentation I can find that the maximum supported for this model is 8GB of RAM (2 x 4GB). Has anyone tried to put bigger DIMMs into one to see if they would work? Given the price of RAM at the moment I would go for 2 x 8GB if I knew it would work.
Your Macbook Pro supports only 8GB (15'') or 6GB (17'') of RAM.
Apple states that it's 4GB, but OWC continuously check the max. supported RAM.
See this list here.