There are two ways to balance basic (LBB1) and extended (LBB4-7) characters, either:
reduce the number of skills the extended character generation produces in line with basic;
or
increas the number of skills awarded from basic character generation.
The second is easily achieved by borrowing a couple of idea from MegaTraveller basic character generation, the rule of four (make a survival, commission, promotion, special duty roll by four or more higher than needed and gain an extra skill for that term), and the inclusion of a special duty target number in the basic generation tables - make the roll and gain an extra skill that term.