Could you please help me with a couple of balance issues.
World Models, Super Sport 40, TT 42GP engine.

Problem, Center of Gravity is 35mm Aft of manufacturers recomendations. all up with an empty fuel tank.

Questions, Do you check CG with an empty tank ?.
To balance as per instructions I will need to load 5<6oz of lead into the front of the plane , IS THIS NORMAL?
How accurate does the CG need to be?

Thanks in advance for the help.