SAP / HE penetration

[Kaiser Kirk]

I was browsing Navweps and Okun's page and came across this :
"The following guns used nose-fuzed projectiles, a type not included in FACEHARD: The US 5"/25; and the Japanese 5"/40, 5"/50, and 3.9"/50. According to Nathan Okun, a nose-fuzed projectile would penetrate 0.2 calibers of homogeneous ductile plate (obliquity not important when filler explodes in most cases) or 0.3 calibers of a face-hardened KC-type plate. Thus a typical 5" gun firing a nose-fuzed projectile would penetrate 1.0" of homogeneous armor or 1.5" of face-hardened armor throughout its range, with most of the penetration from the explosive force of the burster rather than kinetic energy."

Not being base fused, they are not AP. 
So I got to wondering what that meant if you want a light armor belt proof against all but AP ?

So 6" = 1.2" / 1.8" ...

If Homogeneous
25mm – <5"
30mm -  <6"
40mm - <8"
50mm – <9.9"
65mm- <12.8"
75mm – <14.75"

If Facehardened... the lower limit of was about 88-90mm, but most nations stopped at 100mm.
90mm – proof vs. 300mm SAP
140mm – proof vs.  467mm SAP

Elsewhere I've come across information, that if memory serves, 20-25mm is good vs light splinters, 40-50mm against all but major caliber splinters and All HE (which echoes the above vs. all QF mounts), and 2.5"/ 65mm is what the USN felt would stop all major caliber splinters.