Wow, that seems like an awful lot. You only need about a TBS per gallon of water of the premium carbon.
If you stuff your filter media too full with carbon the water won't filter through properly and then you will have water back splashing back into the tank instead of filtering through the media like it's suppose too. It will result in cycling problems.
When it comes to the carbon, less is more and be sure to rinse it in syphoned dirty tank water first.