Armor mastery and DoS max dex bonus not working or stacking?

[IronClan]

Just got DoS II already have Armor Mastery I (Dwarven) yet my max Dex bonus is still sitting at 4... Equipping a +4 dex item takes me from 16 (+3) to 20 (+5) but only results in a loss or gain of 1 AC... (using character sheet mouseover AC breakdown)

Wearing +5 Mithral FP = 3 max Dex bonus
(with or without +5 Mithral Tower which has a 4 max Dex bonus)
Armor Mastery I = +1 to max Dex bonus =4
DoS I = +1 to Tower shield =4 still (but would be 5 if I took off armor and only held the shield)
DoS II = +1 max Dex bonus = 5 (6 if I equipped only a tower)

If I take armor off and only equip the tower I do indeed have a max Dex bonus of 6

Yet I'm only getting 4 ... Already tried logging in and out, taking everything off and putting it back am I missing something undocumented, or what? Does the DoS improvement not stack with the enhancement lines?

[dkyle]

Mithral FP is Medium armor, not Heavy armor. DoS II only adds +1 to max Dex mod for Heavy Armor and Tower Shields. So, you are only benefiting from the armor mastery. DoS III will add +1 to max Dex mod for your mithral FP.

[IronClan]

Mithral FP is Medium armor, not Heavy armor. DoS II only adds +1 to max Dex mod for Heavy Armor and Tower Shields. So, you are only benefiting from the armor mastery. DoS III will add +1 to max Dex mod for your mithral FP.

ah that explains it, well at least it'll help when I get DTFP

[Junts]

indeed, and with dt fp and up you'll have +2 to dex from defender, as it's +3 tower/+2 heavy/+1 med at dos 3.

You'd need really astronomical dexterity to need armor mastery between dos bonuses and epic armors with greater nimbleness; i get 6 max dex out of my red dragonscale fp w/o any armor mastery (as a human).

[unbongwah]

IIRC, DoS I adds +1 MDB to tower shields only; DoS II adds another +1 MDB to tower shields and +1 MDB to heavy armor; and DoS III adds +1 MDB to shields and heavy & med. armor for a total of +3, +2, & +1 MDB, respectively.