And one last related clarification that I think is reasonably related.
Page 124 corrected sixth printing of Total Warfare gives a +2 to critical hit rolls to all industrial mechs.
For those equipped with Commercial Armor does this stack with Penetrating Critical Hits and Armor Piercing Ammunition modifiers?
Oh and the errata referenced repeats what is already stated in the fourth paragraph so the fifth paragraph could be removed entirely and nothing lost.
Almost forgot to thank you for the previous answer too.
Apologies and my thanks xotl.