Hmm, there is "Shield" category too but it doesn't work well in this case.
When I put AC bonus in deflection category it seems to work good. If I put it in "Shield" category, it doesn't increase overall AC. Don't seek too much logic in this, Black Isle lacked time and money (lol
) to make this game perfectly passing quickly from 2nd to 3rd D&D edition and so on. Testing is the only way to find correct procedures.
Some solid shields add double AC bonus to Armor and Deflection categories, others add to that a triple bonus to Armor/Deflection/Shield. More comparisons and testing are necessary to understand all that.
Pliz try my current modification, it seems to work correctly.
Tc, Yigor