I've got a character who is to dual wield tower shields. The challenges are attacking, as well as the feat cost. I've done most of the work on GitP.
In Plot and Poison: A Guidebook to Drow, there is a feat called Double Shielding, which allows you to employ two shields with an armor check penalty of -1 or better (so -1 or 0) and gain the armor bonuses and enchantment bonuses from both shields, while suffering the combined armor check penalty of both shields.
Shield Mastery from the same book explicitly allows you to bash with the mastered shield. Shield Specialization, from this book, not PH2, reduces the check penalty by a -1 (really quite bad for a feat...exceptionally bad really).
So far, if the feats required for this build (Shield Specialization and Shield Mastery, both from Plot and Poison) were to be removed, I would have a -2 ACP on each tower shield, and couldn't shield bash. The ACP being worse than -1 means I couldn't dual wield them either.
The question here: How do I further reduce the ACP and bash with it while keeping the shield bonus to AC, without spending feats? So far I've not been able to find a way. Any published book is allowed.
(I don't care if "tower shields are bad." That's not the question.)