Hm, okay. The problem is, that the game settings file says, that the cannoneers ignore the bonus tower armor. Obivously, they do not ignore 100% of it. As I dont know the exact value, simulations with cannoneers against towers are not reliable anymore.
In a very old file the value was 13%. I do not know if it is still the case, but I will set this value back as default. Please check if the results match with yours now.
And please tell me your exact losses.
Regards