Chess960: What is the weakness of the Patriarch Bishops?

Considering that almost 50% of Chess960 games contain various versions of the Patriarch Bishops it begs the question, what is the weakness of these bishop pairs? They have some obvious strengths:

1. The primary patriarch's are already developed once the pawns clear their path
2. The attack paths are clearly defined but become less clearly defined as the bishop pairs move towards the centre

Ok so here is a summary of the primary weaknesses of the Patriarch's:

1. The bishop pairs cannot defend each other
2. The bishop pairs have no defenses against rank and file attack
3. The bishop pairs have a floating 2x2 square of weakness displaced by one rank immediately above them

The last point is actually the one that has only really come into my experience lately. Here is a very rough example of what point three means:

SP240 Black to play: Exploit the Primary Patriarch's weakness

The green square is what I mean by the "floating 2x2 square of weakness" that the patriarch's have. It is particularly important in Chess960 because that square fundamentally affects the strategy of the patriarch games particularly the primaries (13% of all games).

Black's move that exploits the patriarch weakness is simply ... e6! White has inadvertently completely forgotten about consolidating the c-side. Without consolidation, black can gain access to the undefended squares above the patriarch's and combine checking and capture threats. Note that if white tries to back up b4 with a3, the a3 pawn falls after black plays ....Nb5/a5. So the example above is a good one to show where the primary patriarch weakness is in a practical setting. 

As a primary patriarch chess960 game unfolds, these basic questions arise:

1. Are white's bishops aimed at the enemy king?
2. If they are how is black going to build a fortress?
3. Has a player neglected the 2x2 weak squares above the patriarch bishops?
4. If yes, then the opponent has counter attacking chances on the patriarch's wing.

If you have read this far, then here is some insider information for you!

In Chess960 almost 50% of all games are Patriarch family games. So if you are in a Patriarch 960 game, be aware of counter-attacks on the side of the board that the patriarch's rest. If you can sure up your king defense against bishop onslaught, that is when the counter attack can begin. It relies on the attacker under-defending the 2x2 floating square of weakness that floats above the patriarch bishop pairs.

Enjoy 960