From the armored rogue thread:
* Races of Stone Heavy Armor Optimization and Greater Heavy Armor Optimization increase the armor bonus by 1 each, and reduce the armor check penalties by 1 and 2, respectively, for a total +2 AC and -3 armor check penalty.
* The Nimbleness ability from Magic of Faerun reduces armor check penalties by 1, and increases max DEX by 2.

I don't think the heavy armor thing will work on the tower shield, but I don't have Races of Stone to check the wording.
Nimbleness might be a waste since the shield doesn't have max dex.

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