Armor multiplier

[Fuski]

Armor upgrades remain on the new ship now unless transferred over to be sold with the old ship now. Thankfully.

On an earlier topic, we use both , and . here in the USA. 1,000.25
Which means one thousand and a twenty-fifth. or 1 thousand and a quarter.
Less confusion in reality, so when a . is used to separate numbers then we (god help me with the sense in this nation) would know it's a fraction/decimal
As .5 is half. 1.5, one and a half.

completely unrelated, My question is this:
There are 2 armor upgrades with 2.5. A UAU and a CAU. I've read the description on both. One being cheaper, and taking up less cargo, but the CAU says it protects better than the UAU. So in reality:

Does a 2.5 UAU multiply base hull by x2.5 on a transport/cap ship, or is it more of a x1.5/2.0? Does the UAU give a full benefit to a heavier ship, or do I need to get the CAU x2.5 to get the full x2.5 hull reinforcement?