From what I see there are the DU part numbers; the main weight and an underlying weight and then the new weights for replacement have new numbers and old numbers, shielded and unshielded (See pg. 43). As for the shielding, see pg. 15. DAC offers both. Also see pg. 45, (3), 6/, this apparently...
Kirby,
I'm working the same issue with S/B 55-21. However, after identifying the effectivity, now the question is the intent of the S/B group I vs. group II. Particularly for this S/B, is the intent to first remove the upper rudder or not? Changing the weights with rudder installed seems...