Dell XPS 17 L701X RAM capacity

Hello

I currently have the Dell XPS 17 L701X i7 processor; there are two slots for RAM (current setup: 4GB = 2x2GB) and I wish to upgrade.

Please can someone tell me the maximum capacity of a single slot - I wish to replace one of my sticks of RAM with an 8GB stick so as to achieve 10GB = 8GB + 2GB. Is this possible with my machine? Dellcares on twitter and the pre-sales chat team disagree on their answers. Can anyone clarify once and for all whether it is possible to do this, or whether the max capacity is 4GB per slot?

Thank you