Will I be charged more if I request additional address space?

No. The charges are fixed annual charges, based on the size category of the Local Registry. As a member of the RIPE NCC you are charged based on the services you receive from the RIPE NCC, not on the amount of addresses you obtain. For more information see the current version of the "RIPE NCC Activities, Expenditures, and Charging Scheme" located in the RIPE Document Store.