[DARKBLADEZD73]

Hey Chummers,
                             Need to know if there are any rules in any of the 5th edition books regarding Custom Protection Rules? Do they Stack?

So, if I have SteamPunk Custom Fit w/ Chem Pro. 3, Fire Resist 3 and Thermal Dampening 3, & I am wearing  a Custom Fit (Stack)  Synergist Business Longcoat over that with all the same Custom Protection Mods...Do THEY STACK?
 
   So, would I then have Chem Pro. 6, Fire Resist 6 and Thermal Dampening 6? Please Clarify any actual RAW that cover this topic with Book and Page number. Thank You!

[Xenon]

They don't stack. If you have two pieces of armor, one with less armor rating but insulation and one without then you would use the one with higher armor rating and the other does nothing (in most cases). If you are hit by Cold damage then you might use the armor with less armor rating but having insulation (if it is more favorable for you) - but in this case the one with higher armor rating does nothing.

SR5 p. 169 Armor and Encumbrance
If a character is wearing more than one piece of armor at a time, the value of the highest armor piece applies for determining Armor. All the other pieces do nothing but add a lot of bulk...