Iron Drapes

This is my blog. I don't know if you got confused by the placement of the photo showing the T-72B's armor array, but the text is not related to the T-72B.
The way Mr. Hilmes describes the development of bulging plates armor (sandwich plate NERA) is essentially that people took conventional multi-layered spaced armor, vulancized rubber at the back and added thin steel plates to it. This might be how the first types of NERA were developed in Germany. According too him, the T-72M1M/T-72B's turret armor, the armor essentially acts like spaced armor against APFSDS ammunition and provides no gain in effective protection, no type of similar looking bulging plates armor is supposed to provide enhanced protection against KE.
The statement from the blog was focused on thicker armor components mounted in front of the general NERA arrays that seem to be part of any modern tank. I mentioned the Leopard 2A5 and the Kontakt-5/Relikt ERA of Soviet/Russian tanks as example. The wedge-shaped armor of the Leopard 2A5 for example consists of two to three (depending on location) rather thick (~70 mm) sandwich plates, which supposedly are made of high-hardness steel. Similar NERA sandwiches have been tested in Germany and the Netherlands against APFSDS and shaped charge warheads with great effect.

(This is what a NERA sandwich with two 16 mm HHS plates does to a L/D 20 tungsten rod).
The Soviet Kontakt-5 ERA has an areal density of 500 to 550 kg/m², which equals roughly 60 to 70 mm steel per m², or slightly more steel than two of the NERA sandwiches of the T-72B's turret when seeing the armor array directly from the front. The explosive filler leads to a much greater plate bulging/movement than on the T-72B, making it even more effective.
The values were for shaped charges, not for APFSDS rounds. AMAP-B can have a mass efficiency of 5 against kinetic energy projectiles, but only against bullets. The effiency against large calibre penetrators has to be much lower, otherwise a modern day Leopard 1 would be immune to most 120 mm rounds.
Can you please explain this a bit more? According to R. Lindström, the T-80U send to the Swedish tests had essentially the same armor, just slightly different thickness.

 

Yes, and that is the primary (perhaps only) influence of bulging armour.
From what I know, it depends on what sort of material is used in the sandwich layer. The rate of energy transfer differs from material to material, and some reach their peak very quickly. Best guess is that it is simply a matter of optimization. It would be inherently better to have more spacing, as that would be more efficient in terms of mass, but for bulging armour using certain sandwich materials, it may be more efficient thickness wise to stack them more closely. You have a heavier, but slightly more protective array.
As for arrays with thicker front plates than back plates, that is easily explained. "In pursuit" or "forwards" type NERA armour where the bulging plate expands in the same direction of travel as the projectile is more effective than "In retreat" or "backwards" type NERA armour, where the bulging plate expands against the direction of travel of the projectile. These pictures can tell the tale better than I:
 

 
It would be more beneficial to have a bias in the direction where the NERA plate bulges. In the case of the T-72B, the NERA can only bulge in one direction. The front plate is too thick and too heavy to move at all. More modern designs may be better optimized for certain threats, but I don't really know much in the way of specifics.