Ted :

There are different ways to work on your situation. The best thing for a pond population is year class balance (unless you are managing for a different goal). It is hard to get that in the short term by adding adult LMB and it is a tricky situation. Be sure there are way to many BG before you do to much as most southern ponds tend to be bass crowded (not enough BG)over time. I would not add any more adult LMB without much more info as 20 - 2 lb LMB per acre is a lot in your apparent situation.

Are you sure there are no small LMB under 8 in.?
What does your CNBG population look like (numbers and sizes)? Have you tried a seine survey. Is there a reason to be in a hurry to fix the situation?

You should think about replacing the missing year class rather than just adding adult LMB unless certain specific situations exist wrt your CNBG and LMB spawning. One way is to add 2-4in fingerlings in the fall (Oct.)after it has cooled down. Many may be eaten but there are ways to increase their survival. Another way is to wait until march or April and add advanced fingerlings (6-8 in.). Note in both situations you are replacing the missing year class not just adding adult LMB.