That belt figure for reducing torpedo damage by 80% is wrong.

In my testing I went as far as 11.4" of belt for KM and I got about 60% reduction (
from memory). But you're free to look it up in Tips&Tactics.

According to others belt depth info and torp damage:

Getting to 5 on the HE defense lowers the torp damage by around 80%

UK thats 1.5 belt

KM MN and US is around 1.8 belt.

IJN is like 2.2 Belt.

As far as MN armor not bouncing shells.

ROFL

Try 900 SD on a Richelieu with at lest 8.5 deck and 1.5 belt. You'll bounce shells.

There was a test some time ago that proved, that .2 belt cut torp damage almost half...
more belt reduces torp damage even further, but the effect is almost not noticable and not
worth the weight.

Ok, thanks for the answer

I always go until you get the 1 in HE defence. for MN its .4
Many people say its just .2 for all nations that cuts torp damage in half.

And no MN ships are good for AW really, the BB5 can with 2 guns I guess, but the
armor is not good enough to bounce anything significant.