Compounding Damage/ Customize / 15^50/ +20% vs anything

OK i know that 15^50 weapon customized will do

+35%damage >50 and 20% <50

what if you add a mod like +20%vs charr or whatever does it make it

+55>50 and 40<50 vs charr as the bonus damage.

Yes, you can do UP to 60% against any AI, except humans.
20%<50 + 20% Customzing + 20% vs. ---

It all multiples together, it doesn't add. 1.15 * 1.20 * 1.20 = 1.656, or 165.6% of regular damage when over 50%, and 1.20 * 1.20 = 1.44, or 144% of damage when under 50%.

I never did get the maths behind multiple percentages - off topic, but what if you have two 10% chances of the same thing, or 20% + 10% of the same thing?

Thankies *bows*

Add JI to your build and you will do +120% against undeads

JI turns your weapon damage into holy damage, which is double damage versus undead, not 120%.