i was able to get to 11 without using thick hide. moderate articulated plate+tower shield. 13 with the armor tree. add fitted and light into that and you have no acp speed or defense penalties,
Double check your math.
Moderate A. Plate is DR 5 with -2 ACP and Def and -5 Move.
Heavy Fittings brings it to DR 7, -3 ACP/Def and -10 Move.
Armor B/M/S brings it to DR 9, -2 ACP and Def and -5 Move.
Fitted and Lightweight take it to DR 9, -1 ACP and Def.
Dwarf construction gets you to DR 10, conversely Elf construction lets you skip light weight and gets rid of the ACP penalty.
The Tower Shield would then add 3 to your defense, for a net gain of DR 9, Blunt 2, +2 Def with Elven construction, or DR 10, Blunt 2, ACP -1, Def +2 with Dwarven construction.